Potash Production

1. Potash Production

2. Froth Flotation • Applied surface science • Oil sands • Wastewater • Mineral benefaction.

4. Waxing My Car (a hypothetical experiment)

5. Interactions of a submersed solid with an air bubble:

6. Flotation of Hydrophobic Materials • Talc • sulfur • bitumen • oil • graphite

9. Non-polar Polar Solid Surface Collectors • Selectively render surface of desired mineral hydrophobic. • Surfactants Non-Polar Polar

11. Mechanisms of Collector Adsorption • Poor basic understanding • Mechanisms: • Physical Adsorption • Chemisorption • Weak Electrostatic Interaction • Neutral Molecule Adsorption.

12. Physical Adsorption • dipole-dipole interactions • hydrogen bonding • electrostatic attraction

13. Point of Zero Charge (PZC) • Surface charge often a function of pH • pzc of quartz is 1.9

14. Various pzc values can lead to specificity

16. Chemisorption • Bond formation between collector and mineral.

19. Other Flotation Chemicals • Depressants • Frothers • Extenders

20. Depressants • Inhibit flotation of undesired minerals • Starch, guar depress flotation of clays in potash • depression of copper with Na2S or NaHS for molybdenum recovery

21. Frothers • Stabilize air bubbles so they don’t burst • formation of a foam layer • small chain alcohols • coat air bubbles - lower air/water  • C6 - C10 alcohols used in potash

22. Extenders • Improve recovery of desired mineral • non-polar liquids • in potash, use heavy oil (fused ring aromatics) • extenders improve recovery of larger particles • mechanism unknown

23. Potash Processing • Saskatchewan has immense reserves of potash • nameplate capacity of 20 M tonnes/year • 10 plants • 7 plants use flotation

24. Rocanville, Sask. Sussex, N.B

25. Devonian Period, -350 Ma • Sea water concentrated • Chloride salts crystallized in sequence • Now buried by 1000 m of sediments • Seas covered continent • Mountain uplift, then cutoff • Solar evaporation concentrated brine

28. Ore Mineralogy • Composition: • NaCl: 55% • KCl: 35-40% • KMgCl3.6H2O: 1-5% • Insolubles: 1-8% • Size Range of Natural Crystals in Ore: • 1-10 mm 3 mm Discrete KCl/NaCl/insoluble particles

29. Crushing & Grinding • Dry crushed to - 8 mm • crushing with hammer mills • crushed ore passed through screens • wet grinding in rod mills or cage mills • ground ore classified by screen or cyclone • Ground to < 4 mm • Ground to the “liberation size” • closed circuits

33. Desliming • series of agitated tanks (scrubbers) • clays scrubbed from ore surface • insolubles separated by cyclone or flotation • dirty brine sent to thickener • clean brine recycled • U/F discarded

38. Ore conditioning • Depressants • inhibit flotation of residual clays. • Starch, guar, carboxymethylcellulose (CMC) • conserves amine • Collector • CH3(CH2)17NH3+ • selectively coats KCl particles • exact mechanism unknown

41. Ore Conditioning • Extender • heavy oil (fused aromatics) • added with the collector • Frother • C6-C10 aliphatic alcohols • stabilizes the product froth

42. Ore Conditioning • Ore slurry is mixed to provide good coverage of reagents. • Frother added just prior to flotation.

43. Flotation Equipment • Conditioned feed, 20-40% solids • 3 to 6 cells in series forms one bank • each cell has an agitator, air injection • froth collected from top by paddles • gangue flows through cells

45. Bubble-solid interactions agitation zone: • bottom of the cell • bubbles dispersed by agitator • bubbles adhere to surface of desired mineral. quiescent zone: • intermediate depths • agitation is less vigorous. • air bubbles carry the desired mineral up • unfloated material flows on to the next cell

46. Bubble-solid interactions concentration zone: • top of the cell • froth enriched in the desired mineral • product collected by paddles • flows into a collection launder

47. Mineral Flotation Cell

48. Flotation • Amine-treated KCl collected from top of cells • product is 95% KCl • waste salt flows through cells and is discarded.