Craig Walker, Weir Minerals - Pump selection for slurry transport applications

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Dr Craig Walker, Managing Director, Weir Minerals Australia and Paul Fitzgerald, Regional Manager GEHO Australasia, Weir Minerals presented this at the 3rd Annual Slurry Pipeline Conference. The Conference focuses on the design, construction, operation and maintenance of mineral slurry pipelines.

For more information, visit http://www.informa.com.au/slurrypipelineconference

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Craig Walker, Weir Minerals - Pump selection for slurry transport applications

  1. 1. Pump selection for slurry transport applications Craig Walker, Consultant, Weir Minerals Australia Jos Sloesen, Regional Manager GEHO / Industry Manager Long Distance Pipelines
  2. 2. Pump selection for slurry transport applications 2 Outline  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 Slurry transport by flumes was documented as early as the 16th century
  3. 3. Pump selection for slurry transport applications Slurry pumps for pipeline transport  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 Pump reliability is key to cost efficient pipeline transport of solids 3
  4. 4. Pump selection for slurry transport applications Material transportation alternatives  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 Economics and environment need consideration in material transport 4
  5. 5. Pump selection for slurry transport applications Pipeline Transportation of solids  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 Slurry pipeline transport is often lower cost than alternatives 5
  6. 6. Pump selection for slurry transport applications 6 Trends in long distance slurry pipelines Length of pipelines is increasing More pipelines with multiple pump stations (2, 3 or even 4) Pipeline throughput increasing Slurry pipeline length and capacity requirements keep increasing
  7. 7. Pump selection for slurry transport applications 7 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 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) Environmental safety and water usage are pressing issues for miners
  8. 8. Pump selection for slurry transport applications 8 Alternative slurry pumping equipment  Centrifugal pumps  Impeller rotates to generate head  Variable flow depending on pump system interaction  Positive Displacement (PD) pumps  Piston reciprocates in cylinder to generate flow  Fixed flow per stroke  Low pressure but high flow compared to PD pump  High pressure but reduced flow compared to centrifugal pump  7 MPa and 7000 m3/h  30 MPa and 1000 m3/h  Multi-staged to generate pressure  Parallel pumps to generate high flow Pump type selection depends on pressure and flow requirements
  9. 9. Pump selection for slurry transport applications 9 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 Coarse slurries require higher velocity Finer slurries can be pumped more slowly 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 20 to 7,000 m3/h 10 to 1000 m3/h 80 m for fine particles and 55 m for coarse particles Up to maximum pump pressure rating 8 n/a Flush water Yes No Capital cost Low to medium (depending on stages) High 70 to 85% depending on de-rating factors 90 to 95% crankshaft drive Pipeline settling velocity Slurry density Flow Max. head per stage Max. number of stages Efficiency
  10. 10. Pump selection for slurry transport applications 10 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
  11. 11. Pump selection for slurry transport applications 11 Design and application guidelines - Centrifugal Pumps  Examples in oil sands hydrotransport        Two stages of 550SHD 5700 m3/hr 110m head 100mm lump with sand SG=1.65 P=1800 kW motors Canada  Two stages of 600HTP  100mm lump with sand  Canada Centrifugal pumps can handle large particle sizes e.g. 100mm
  12. 12. Pump selection for slurry transport applications 12 Design and application guidelines - Centrifugal Pumps  Examples in iron sand concentrate        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      Undersea pipeline D=300mm nominal Length=5km Velocity=5m/s 130,000T bulk carrier Centrifugal pumps can handle heavy particles e.g. SG=4.1
  13. 13. Pump selection for slurry transport applications 13 Design and application guidelines - Centrifugal Pumps  Examples in tailings transport        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 Fine tailings can be pumped medium distances with centrifugal (>8km)
  14. 14. Pump selection for slurry transport applications 14 Design and application guidelines - Centrifugal Pumps  Examples in tailings     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 Multiple pump trains offer flexibility and reliability for tailings system
  15. 15. Pump selection for slurry transport applications 15 Design and application guidelines - Centrifugal Pumps  Example for tailings  4 stages 20/18AHP  Sand tailings  Canada       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)
  16. 16. Pump selection for slurry transport applications 16 Design and application guidelines - Centrifugal Pumps  Materials of construction     Hypereutectic white iron with patented refined microstructure Laser applied tungsten carbide coatings High resilience nano-particle filled rubbers Composite ceramics New material advances increase pump life and availability
  17. 17. Pump selection for slurry transport applications 17 Design and application guidelines - Centrifugal Pumps  Head and efficiency de-rating     HR = Hw/Hs ER = Ew/Es Best to be conservative Non-Newtonian slurries use different procedure
  18. 18. Pump selection for slurry transport applications 18 Design and application guidelines - Centrifugal Pumps  To generate higher pressure for pipelines, centrifugal pumps must be staged A sequenced pump start-up to gradually fill the pipeline is important to prevent motor overloading or cavitation Up to 8 stages of centrifugal pump can be used in one station
  19. 19. Pump selection for slurry transport applications 19 Design and application guidelines - Centrifugal Pumps  Pump station layout alternatives    Best maintenance access from rear Interstage piping has inherent flex Wear in pipe bend can be an issue Pumps with parallel shafts and drives     Pumps with right angle shafts and drives Right angle shaft layouts more popular for centrifugal slurry pumps Smallest layout footprint Interstage piping requires an adjustable joint Alternate pump sets raised Alternate top and bottom discharge
  20. 20. Pump selection for slurry transport applications Design and application guidelines - Centrifugal Pumps  For high yield stress slurries, use a flow inducer style impeller on the first stage  8km pipeline with 5 stages of pumps  first stage 8MF inducer style  d50 = 0.02mm particle Flow inducer impellers can handle high slurry yield stress >70Pa 20
  21. 21. Pump selection for slurry transport applications 21 Design and application guidelines - Centrifugal Pumps  Gland water system design       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 Gland water system design is critical to reliable multi-stage applications
  22. 22. Pump selection for slurry transport applications 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 22
  23. 23. Pump selection for slurry transport applications Design and application guidelines – Positive Displacement 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 23
  24. 24. Pump selection for slurry transport applications Design and application guidelines – Positive Displacement pumps 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 24
  25. 25. Pump selection for slurry transport applications Trends in PD pumping equipment Pump power frame output has been growing strongly over last 30 yrs 25
  26. 26. Pump selection for slurry transport applications 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 26
  27. 27. Pump selection for slurry transport applications Pressure pulsations, two pumps on one pipeline Pressure pulsations a problem with PD pumps if not well handled 27
  28. 28. Pump selection for slurry transport applications 28 Pump synchronisation Effect on synchronization 20 Pressure pulsation, [bar p2p ] Un-synchronized Synchronized 15 10 5 0 10 15 20 25 30 35 40 Stroke rate, [spm] 45 50 55  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 60
  29. 29. Pump selection for slurry transport applications Pump station layout System architecture of PD pump synchronisation 29
  30. 30. Pump selection for slurry transport applications 30 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)
  31. 31. Pump selection for slurry transport applications 31 Examples – Pipeline with PD pumps 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)
  32. 32. Pump selection for slurry transport applications 32 Examples – Pipeline with PD pumps 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)
  33. 33. Pump selection for slurry transport applications 33 Examples – Pipeline with PD pumps 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
  34. 34. Pump selection for slurry transport applications 34 Examples – Pipeline with PD pumps 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
  35. 35. Pump selection for slurry transport applications 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 35

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