equipment selection for hpgr-based comminution circuits part 1 –chris_morley

Equipment Selection for HPGR-Based Comminution Circuits – Part 1 | 16 October 2013 | 1

Equipment Selection for HPGR-

Based Comminution Circuits

Part 1 – Stage Crushing

Chris Morley | 16 October 2013


Presentation Structure

Part 1

• Introduction

• Blasting

• Primary Crushing

• Secondary Crushing

• Coarse Screening

• HPGR

• Fine Screening

Part 2

• Introduction

• Ball Milling

• Cyclone Feed Pumping

• Cyclone Classification

• Materials Handling

• Dust Control

• Tramp Metal Management


Introduction

• Stage-crushing superseded by AG/SAG technology some

decades ago

• Stage-crushing plant design expertise/experience lost

• HPGR marks return to stage-crushing plant design

• Need for resurrection of equipment selection rules and

plant design practice guidelines

• Previous papers addressed flowsheet and layout issues

• This presentation focuses on equipment selection: - Part 1 – stage crushing

- Part 2 – milling and ancillary operations


Blasting

Relative Costs

1. SAG milling

2. Blasting

3. Crushing

Hence:

• High-intensity blast for

SAG-based circuits

(‘mine to mill’)

• Low-intensity blast for

stage-crushing circuits


Primary Crushing

Rationale

• Capacity = ƒ(ROM PSD)

• ROM PSD = ƒ(RQD, blast)

• More costly to blast than to

crush, therefore

• Use low-intensity blast to

miminise blast-crush

opex

• Blast optimisation study


Secondary Crushing

Circuit Design

• Closed circuit essential for

HPGR feed top size control

• Reverse closed circuit (RCC)

for fines-rich primary crusher

product

• Forward closed circuit (FCC)

for fines-lean primary product,

to avoid arduous screening

duty. Can safely use where: - % -CSS < 35

- % -½ CSS < 20

RCC

PRIMARY

CRUSHING

SCREENSECONDARY

CRUSHING

O/S

U/S

SECONDARY

CRUSHING

COARSE

SCREENING

U/S

O/S

PRIMARY

CRUSHING

FCC


Secondary Crushing

Crusher Selection

• RCC – use brochures for capacity and product sizing at

selected CSS

• FCC – rare, and therefore difficult to benchmark:

- Use conservative target for CSS

- Use minimum brochure values for capacity

- Estimate product sizing:

% -½ CSS in feed is ‘fall-through’

% +½ CSS crushed per brochure

Product sizing = weighted average

• Apply derating for high CWi – eg, Derate = (16/CWi)0.5


Coarse Screening

• Banana screens for high unit capacity, low footprint

- Single deck for FCC

- Double deck for RCC

• Sized using traditional calculations for horizontal and

conventional inclined screens, then

• Apply ‘banana’ factor

- As low as 55% for easily screened materials

- Typical range 60-65%

- Derate bottom deck by 10-15%


HPGR

Testwork

• Population still low on hard

rock, so benchmarking

difficult

• Ore- and duty-specific

testwork required:

- specific capacity

- specific energy

- product sizing

- product flake competency

- product grindability

- roll wear life

• Flowsheet options:

- Open or closed circuit

- RCC or FCC

- Fixed or variable speed

rolls

• Testwork program must

replicate intended

flowsheet


HPGR

Model Selection

• Unit capacity is the

product of:

- Specific capacity

( or ‘m-dot’)

- Roll diameter

- Roll width

- Roll speed

• Capacity scale-up

- m-dot originally linear

- now up to ~1.2 depending

on relative machine sizes

• Roll speed rules

- Umax = 1.35*D0.5 (Lim)

- Speed (m/s) = diameter (m)

- Speed (rpm)

20-22 nominal

23 max

- Roll speed rules becoming

less conservative. For 2.4 m

diameter:

Lim 2.1 m/s

m/s = m 2.4 m/s

23 rpm 2.9 m/s

m.


Stage Crushing – General

• For multiple modules

- Largest available machines

economies of scale

- Abrasive ores short Mn

wear life spare

secondary crusher

- Provision in layout for

additional module –

debottlenecking

• For smaller-scale

applications

- Match number and size to

duty

- Turn-down requirements

- Spare units?

Secondary crushers, HPGRs, coarse screens:


Fine Screening

• Banana screens for high

unit capacity, low footprint

- Mode

Dry

Wet

- Decks

Single – suitable for HPGR

product screening

Double – unnecessary and

detrimental

• Sized as for coarse

screens; however

- High circulating load

large bed depth

- Dual (wet) screens per

mill

To control bed depth

To avoid mill shutdown

for screen maintenance

To provide sufficient

area for reduction in cut

size for HPGR-mill load

balancing


Conclusion

• Stage-crushing plant equipment selection addressed in

Part 1:

- Blasting

- Primary crushing

- Secondary crushing

- Coarse screening

- HPGR

- Fine screening

• Ball milling and ancillary operations in Part 2


Equipment Selection for HPGR-

Based Comminution Circuits

Part 1 – Stage Crushing

Chris Morley | 16 October 2013

Thank You

equipment selection for hpgr-based comminution circuits part 1 –chris_morley

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