scale-up of laboratory grinding and flotation tests … · scale-up of laboratory grinding and...

SCALESCALE--UP OF LABORATORY GRINDING UP OF LABORATORY GRINDING AND FLOTATION TESTS FOR PLANT AND FLOTATION TESTS FOR PLANT

DESIGN AND OPTIMISATIONDESIGN AND OPTIMISATION

Brian Loveday

Laboratory tests provide a Laboratory tests provide a means for precise research and means for precise research and

routine ore assessment. routine ore assessment.

How useful are these tests for How useful are these tests for prediction of plant performance prediction of plant performance

and plant optimisation??and plant optimisation??

ScaleScale--up of ballup of ball--millingmilling

nn The Bond Lab. Test is well established, The Bond Lab. Test is well established, but but labourlabour intensive, performed dry, the intensive, performed dry, the screen recycles hard (not dense) minerals, screen recycles hard (not dense) minerals, and it produces a narrow size distributionand it produces a narrow size distribution

ScaleScale--up of ballup of ball--millingmilling

nn The Bond Lab. Test is well established, The Bond Lab. Test is well established, but but labourlabour intensive, performed dry, the intensive, performed dry, the screen recycles hard (not dense) minerals, screen recycles hard (not dense) minerals, and it produces a narrow size distributionand it produces a narrow size distribution

nn The concept of a Work Index is good, but The concept of a Work Index is good, but simple (wet) batch tests can produce simple (wet) batch tests can produce similar information.similar information.

ScaleScale--up of ballup of ball--millingmilling

nn The Bond Lab. Test is well established, The Bond Lab. Test is well established, but but labourlabour intensive, performed dry, the intensive, performed dry, the screen recycles hard (not dense) minerals, screen recycles hard (not dense) minerals, and it produces a narrow size distributionand it produces a narrow size distribution

nn The concept of a Work Index is good, but The concept of a Work Index is good, but simple (wet) batch tests can produce simple (wet) batch tests can produce similar information.similar information.

nn The forces in the laboratory mill are smallThe forces in the laboratory mill are small

Breakage MechanismsBreakage Mechanisms

nn Breakage occurs by impacts or Breakage occurs by impacts or compression between balls. Thin compression between balls. Thin fragments and sharp edges are removed fragments and sharp edges are removed by local impacts (crumbling)by local impacts (crumbling)

Breakage MechanismsBreakage Mechanisms

nn Breakage occurs by impacts or Breakage occurs by impacts or compression between balls. Thin compression between balls. Thin fragments and sharp edges are removed fragments and sharp edges are removed by local impacts (crumbling)by local impacts (crumbling)

nn The compression force required for The compression force required for complete breakage is (mass)complete breakage is (mass)0.660.66

(diameter)(diameter)22 xx--sectional areasectional areaα

α

α α

Lab.Lab. Data on dry grinding (Austin)Data on dry grinding (Austin)

51m m 38m m

32m m 25m m

19m m

0 .1 10 5 1 0 .5

1 .0

0 .1

Partic le S ize, m m

Spec

ific

Rat

e of

Bre

akag

e S i

, Min

ute-1

B all S ize

Effect of ball size on number of contact points and forces

Observations on batch testsObservations on batch tests

nn Addition of water has no effect (the theory Addition of water has no effect (the theory of ball coating is speculation)of ball coating is speculation)

nn Laboratory milling efficiency is adversely Laboratory milling efficiency is adversely affected by high pulp viscosityaffected by high pulp viscosity

nn Hence, use a relatively low solids Hence, use a relatively low solids concentration and measure power concentration and measure power (torque) on all routine tests.(torque) on all routine tests.

Basics of flotation scaleBasics of flotation scale--upup

nn Surface air flux (velocity) is kept constant Surface air flux (velocity) is kept constant (typically: 1(typically: 1--2 cm/sec or 0,6 2 cm/sec or 0,6 --1,2 m/min)1,2 m/min)

Basics of flotation scaleBasics of flotation scale--upup

nn Surface air flux (velocity) is kept constant Surface air flux (velocity) is kept constant (typically: 1(typically: 1--2 cm/sec or 0,6 2 cm/sec or 0,6 --1,2 m/min)1,2 m/min)

nn Air flow/unit vol. (and power/unit vol.)Air flow/unit vol. (and power/unit vol.)vol.vol.--0.33 0.33 cell dimensioncell dimension--1 1 (height(height--11))α α

Basics of flotation scaleBasics of flotation scale--upup

nn Surface air flux (velocity) is kept constant Surface air flux (velocity) is kept constant (typically: 1(typically: 1--2 cm/sec or 0,6 2 cm/sec or 0,6 --1,2 m/min)1,2 m/min)

nn Air flow/unit vol. (and power/unit vol.)Air flow/unit vol. (and power/unit vol.)vol.vol.--0.33 0.33 cell dimensioncell dimension--1 1 (height(height--11))

nn Bubble path length cell heightBubble path length cell heightα

α

α α

Basics of flotation scaleBasics of flotation scale--upup

nn Surface air flux (velocity) is kept constant Surface air flux (velocity) is kept constant (typically: 1(typically: 1--2 cm/sec or 0,6 2 cm/sec or 0,6 --1,2 m/min)1,2 m/min)

nn Air flow/unit vol. (and power/unit vol.)Air flow/unit vol. (and power/unit vol.)vol.vol.--0.33 0.33 cell dimensioncell dimension--1 1 (height(height--11))

nn Bubble path length cell heightBubble path length cell heightnn Hence bubble loading cell heightHence bubble loading cell heightα

α αα

Basics of flotation scaleBasics of flotation scale--upup

nn Surface air flux (velocity) is kept constant Surface air flux (velocity) is kept constant (typically: 1(typically: 1--2 cm/sec or 0,6 2 cm/sec or 0,6 --1,2 m/min)1,2 m/min)

nn Air flow/unit vol. (and power/unit vol.)Air flow/unit vol. (and power/unit vol.)vol.vol.--0.33 0.33 cell dimensioncell dimension--1 1 (height(height--11))

nn Bubble path length cell heightBubble path length cell heightnn Hence bubble loading cell heightHence bubble loading cell heightnn Equivalent kinetics for lean ores?Equivalent kinetics for lean ores?

αα

α

α

Comparison of bubble loadingComparison of bubble loading

nn Batch cell (5L): Relative loading =1Batch cell (5L): Relative loading =1nn PilotPilot--plant cell (50L) plant cell (50L) RelRel. loading =2,2 . loading =2,2 nn Plant cell (50 mPlant cell (50 m33 ) ) RelRel. loading = 22. loading = 22

nn Rate of flotation in the plant is about half Rate of flotation in the plant is about half that in a lab cell (Correction factor = 0,5) that in a lab cell (Correction factor = 0,5)

Comparison of performance

30

40

50

60

70

80

90

0 2 4 6 8

Cum. Mass (%)

Pt. R

ec. (

%)

Plant

Pilot plant

CorrectedBatch dataBatch Data

Application of Models

Kelsall Model (1961)

k2k10Rate Constant

a2a1a0Mass Fraction

Fast-Floating

Slow-Floating

Non-Floating

Can we use batch data to model a plant, by applying corrections?

n Batch tests can be done on samples of feed, concentrate, tails, etc. and Nodal Analysis can be applied

n This demonstrates that batch flotation rates are maintained – However it does not prove that the plant behaves in the same way

Data from the Cominco Red Dog Lead Cleaning Circuit (Runge et al, 1997)

0.70.560.780.060N.S. Gangue

0.850.680.510.039Pyrite

0.850.680.680.053Sphalerite

10.8010.077Galena

Rel. to Pb

Scale-upRel. to Pb

Scale-up

Cl. Scav. ( 2 x OK38)

Final Cleaner (Column)

Observations on fitting batch data to a plant mass balance

n The Red Dog data showed that the separations achieved in the batch tests were significantly worse than the plant

Observations on fitting batch data to a plant mass balance

n The Red Dog data showed that separations achieved in the batch tests were significantly worse than the plant

n The use of different scale-up factors for each mineral, allows the model to fit the base case mass balance (a force fit)

Observations on fitting batch data to a plant mass balance

n The Red Dog data showed that separations achieved in the batch tests were significantly worse than the plant

n The use of different scale-up factors for each mineral, allows the model to fit the base case (a force fit)

n Prediction of the performance of a new circuit configuration would be difficult

Is there another option??

Platinum Flotation CircuitPlatinum Flotation Circuit

SR1

PC2

SR2

PC3 PC1

SC1SC2

PR2PR1

RegrindFeed Feed 2

H.G. Conc.L.G.Conc.

Ro.Tail

Cl.Tail