craig walker, weir minerals - pump selection for slurry transport applications

Pump selection for slurry transport applications

Craig Walker, Consultant, Weir Minerals Australia

Jos Sloesen, Regional Manager GEHO / Industry Manager Long Distance Pipelines

2 Pump selection for slurry transport applications

Slurry pumps for pipeline transport Craig Walker

How to select slurry pipeline pumps Craig Walker

Design and application guidelines

Centrifugal pumps Craig Walker

Positive Displacement pumps Jos Sloesen

Conclusions Jos Sloesen

Outline

Slurry transport by flumes was documented as early as the 16th century


Slurry transport applications

Mineral tailings disposal

Backfill

Ore or concentrate transfer

Ore hoisting

Dredging

Primary requirement for transport pumps

High pressure rating

Long life

Reliable operation

Slurry pumps for pipeline transport

Pump reliability is key to cost efficient pipeline transport of solids


Mine deposits more and more in remote areas (longer distances)

Mine size and throughput increasing

Solids concentration increasing (water scarce)

Regulatory environmental and economic constraints increasing

Transport alternatives (from one to hundreds of kilometers)

Railway

Truck

Barge

Conveyor belt

Pipeline

Material transportation alternatives

Economics and environment need consideration in material transport


Low operational costs

Lowest energy consumption (kWh / tonnage / km)

Flexible in routing (mountains, bypasses)

Does require fluid carrier (water)

Operation

No dust, noise, traffic congestion

Risk of accidents reduced

Not climate or weather dependant

Invisible if burried

Sometimes water return/supply lines required

Short / Medium / Long distance

Pipeline Transportation of solids

Slurry pipeline transport is often lower cost than alternatives


Trends in long distance slurry pipelines

Pipeline throughput increasing

Slurry pipeline length and capacity requirements keep increasing

Length of pipelines is increasing

More pipelines with multiple pump stations (2, 3 or even 4)


Trends in slurry pipelines (continued)

Mining industry slurry pipelines

2012: total 8.107 km in operation

2020: total ±13.000 km estimated in

operation

Pipeline integrity is high on everybody’s

agenda

More tailings being transported through

slurry pipelines

Environmental safety and water usage are pressing issues for miners

High density tailings is now common practice

Water savings

Less space required

Land reclamation possible

Less mechanical requirements to dams

Low risk of dam failure (safety / environmental)


Alternative slurry pumping equipment

Centrifugal pumps

Impeller rotates to generate head

Variable flow depending on pump

system interaction

Low pressure but high flow compared

to PD pump

7 MPa and 7000 m3/h

Multi-staged to generate pressure

Positive Displacement (PD) pumps

Piston reciprocates in cylinder to

generate flow

Fixed flow per stroke

High pressure but reduced flow

compared to centrifugal pump

30 MPa and 1000 m3/h

Parallel pumps to generate high flow

Pump type selection depends on pressure and flow requirements


Pump selection methodology

Parameter Centrifugal Pump (series) Positive Displacement Pump

d50 particle size < 2 mm OK OK

2mm < d50 OK 6-8 mm maximum for large pumps

Pipeline settling velocity Coarse slurries require higher velocity Finer slurries can be pumped more slowly

Slurry density High concentration can reduce developed

head (HR effect)

OK

Slurry rheology Yield stress < 50 Pa with std impeller, but up

to 200 Pa with flow inducer style

If feed to PD is good then no issue with pump

performance

Pressure rating 7 MPa 30 MPa

Flow 20 to 7,000 m3/h 10 to 1000 m3/h

Max. head per stage 80 m for fine particles and 55 m for coarse

particles

Up to maximum pump pressure rating

Max. number of stages 8 n/a

Flush water Yes No

Capital cost Low to medium (depending on stages) High

Efficiency 70 to 85% depending on de-rating factors 90 to 95% crankshaft drive


Design and application guidelines - Centrifugal Pumps

Double wall pump features

Pressure rating of the pump casing does not change as the pump wears. An unlined (single wall) pump design will have lower pressure capabilities as the casing wears

With double wall pump the inner liners are not part of the outer pressure casing. Erosion resistant hard metal alloys and / or elastomers can be used interchangeably depending on the slurry characteristics

External casing of double wall pump takes the piping loads (which can be significant)

Double wall pumps are safer and offer more wear material choices



Examples in oil sands hydrotransport

Centrifugal pumps can handle large particle sizes e.g. 100mm

Two stages of 600HTP 100mm lump with sand Canada

Two stages of 550SHD 5700 m3/hr 110m head 100mm lump with sand SG=1.65 P=1800 kW motors Canada



Examples in iron sand concentrate

Centrifugal pumps can handle heavy particles e.g. SG=4.1

Undersea pipeline D=300mm nominal Length=5km Velocity=5m/s 130,000T bulk carrier

2 trains of 7 stage 12/10AHP Q=1300 m3/hr H=5MPa D50=0.3mm iron sand SG slurry=1.61 P=750 kW motors New Zealand



Examples in tailings transport

Fine tailings can be pumped medium distances with centrifugal (>8km)

Five stages of 10/8AHPP Q=420 m3/hr d50=20micron SG=1.66 Pipeline length=8km Desanded (fine) tailings Australia

2 trains of 7 stages12/10AHPP Q=1200m3/h Copper tailings Peru


Design and application guidelines - Centrifugal Pumps Examples in tailings

Multiple pump trains offer flexibility and reliability for tailings system

Two trains of 7 stages of 10/8TAHP 4.4 Mpa working pressure Gold tailings Indonesia

4 trains of 4 stage 12/10TAHPP AHF first stage 70Pa yield stress slurry Iron ore (desanded) tailings Australia



Example for tailings

Two trains of eight stages 12/10AHPP

Discharge pressure = 6.9Mpa

Pumping distance = 10 km

Total head = 350 m

Copper tailings

Iran

Centrifugal pumps can develop high pressure (>7MPa)

4 stages 20/18AHP Sand tailings Canada



Materials of construction

New material advances increase pump life and availability

Hypereutectic white iron with patented refined microstructure Laser applied tungsten carbide coatings High resilience nano-particle filled rubbers Composite ceramics



Head and efficiency de-rating

HR = Hw/Hs ER = Ew/Es Best to be conservative Non-Newtonian slurries

use different procedure



To generate higher pressure for pipelines, centrifugal pumps must be staged

Up to 8 stages of centrifugal pump can be used in one station

A sequenced pump start-up to gradually fill the pipeline is important to prevent motor overloading or cavitation



Pump station layout alternatives

Pumps with parallel shafts and drives

Pumps with right angle shafts and drives

Right angle shaft layouts more popular for centrifugal slurry pumps

Best maintenance access from rear

Interstage piping has inherent flex

Wear in pipe bend can be an issue

Smallest layout footprint Interstage piping requires an

adjustable joint Alternate pump sets raised Alternate top and bottom

discharge



For high yield stress slurries, use a flow inducer style impeller on the first stage

Flow inducer impellers can handle high slurry yield stress >70Pa

8km pipeline with 5 stages of pumps first stage 8MF inducer style d50 = 0.02mm particle



Gland water system design

Gland water system design is critical to reliable multi-stage applications

Multi-stage centrifugal pumps operate at different pressures Individual gland water pumps required for each stage Ideally PD pumps used to ensure consistent gland flow Alternatively multi-stage centrifugal with flow control Pressure and flow monitoring important for reliability Water quality important for optimum system life


Design and application guidelines – Positive Displacement pumps

Earlier pipelines executed with plunger/piston pumps

Since 1980’s major iron ore pipelines are operated with piston diaphragm pumps

Long distance pipelines now use large piston diaphragm slurry pumps



Plunger / Piston pumps

Medium wear due to:

Direct contact with abrasive slurry

Many wear parts

Piston

Seals

Cylinder liner

Valves

(Gland packing)

High stroke rate

Medium efficiency, medium energy costs

Flush water required (plunger pumps)

Plunger and piston pumps can see medium wear in slurry applications


Piston diaphragm pump is designed to

handle abrasive solid/water mixtures

Low wear due to:

Physical separation between abrasive

slurry and moving parts

Very few wear parts (valves)

Low stroke rate

High efficiency (up to 96%), low energy

costs

No flush water requirements

High discharge pressure available (up to

300 bar)

High pump availability (>98%)

High pipeline availability


Piston diaphragm pumps best for long slurry pipeline applications


Trends in PD pumping equipment

Pump power frame output has been growing strongly over last 30 yrs


Requirements of PD pumping equipment

Larger pumps:

Capacity

Pressure

Unlimited upscaling impossible due to technology limitations

Requires “Out-of-the-Box” innovative solutions

Multiple pumps in pumping station requires understanding of interference

Innovative technology solutions required for larger high pressure pumps


Pressure pulsations, two pumps on one pipeline

Pressure pulsations a problem with PD pumps if not well handled


10 15 20 25 30 35 40 45 50 55 600

5

10

15

20Effect on synchronization

Stroke rate, [spm]

Pre

ssure

puls

ation,

[bar p

2p]

Un-synchronized

Synchronized

Pump synchronisation

Installations with multiple PD pumps are susceptible to excitation of hydraulic

resonances. This depends on phase shift between individual crankshafts.

Pump synchronization controls phase shift and eliminates excitation of

resonances. This significantly reduces pressure pulsation levels.

Uniform flow can be achieved with proper pump synchronisation


Pump station layout

System architecture of PD pump synchronisation


Examples – Pipeline with PD pumps

Construction of Anglo American Minas Rio - Brazil Pump Station 2

Longest Iron Ore Pipeline Worldwide 25 MTPY – 550 km

10x GEHO TZPM 2000 Pumps

Longest iron ore concentrate pipeline in world (550km)



Construction of Toromocho - Peru Largest PD pumps station for tailings worldwide

117,000 Tonnes Cu ore/day 10x GEHO TZPM 2000 Pumps

Largest tailings PD pumping system world wide (117,000 tpd)



Mineracao Paragominas - Brazil First Bauxite Pipeline Worldwide

13,5 MTPY - 245 km 6x GEHO TZPM 2000 Pumps

Meanwhile expanded:

7x GEHO TZPM 2000 Pumps 6x GEHO TZPM 2000 Pumps (new station)

First long distance bauxite pipeline world wide (245km)



Da Hong Shan - China Most complicated Iron Ore Pipeline Worldwide

Build in 4 stages Final set up

4 Pump stations 11x GEHO TZPM 1600 8x GEHO TZPM 2000

Extension and expansion of pipeline - pump system in stages



Samarco – Brazil Followed the trend

Pipeline #1 Plunger pumps Pipeline #2 GEHO Piston Diaphragm pumps Pipeline #3 GEHO Piston Diaphragm pumps

Picture: construction of pipeline #3

2x6 GEHO TZPM2000

PD pump technology trend followed in stages over many years


Summary

Slurry pipeline transportation is a mature mode of transportation, proven

and widely accepted

Long distance slurry pipeline design requires specialists (two phase

transportation)

Centrifugal pumps commonly used for:

Short distance pipelines (<10km)

Coarse particles (<100mm)

Positive displacement pumps commonly used for:

Long distance pipelines (>100km)

Fine particles (<6mm)

Pumping equipment is getting larger to cater for higher flow rates

Unlimited upscaling is not possible – step changes will be required

The design of pumps must focus on maximum availability/reliability

craig walker, weir minerals - pump selection for slurry transport applications

Business

pump casing

pump wears

transport pumps high

pd pump high pressure

transport alternatives

multiple pump stations

velocity slurry densityflow

pressure parallel pumps