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Lecture 10 – MINE 292 – 2013. Free Settling Ratio If F.S.R is greater than 2.5, then effective separation can be achieved If F.S.R is less than 1.5, then.

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Presentation on theme: "Lecture 10 – MINE 292 – 2013. Free Settling Ratio If F.S.R is greater than 2.5, then effective separation can be achieved If F.S.R is less than 1.5, then."— Presentation transcript:

1 Lecture 10 – MINE 292 – 2013

2 Free Settling Ratio If F.S.R is greater than 2.5, then effective separation can be achieved If F.S.R is less than 1.5, then effective separation cannot be achieved For fine particles that follow Stokes Law (< 50 microns)

3 Free Settling Ratio If F.S.R is greater than 2.5, then effective separation can be achieved If F.S.R is less than 1.5, then effective separation cannot be achieved For coarse particles that follow Newtons Law

4 Free Settling Ratio Always aim to achieve separation at as coarse a size as possible If significant fines content, then separate and process separately 1. Consider a mixture of fine galena and fine quartz particles in water F.S.R. = [(7.5 – 1)/(2.65 – 1)] 0.5 = 1.99 So a fine galena particle will settle at the same rate as a quartz particle that is about twice as large in diameter 2. Consider coarse galena and coarse quartz particles in water F.S.R. = (7.5 – 1)/(2.65 – 1) = 3.94 So a coarse galena particle will settle at the same rate as a quartz particle that is about four times as large in diameter

5 Free Settling Ratio General Guideline: If F.S.R. = 3.0, one can assume an efficiency of about 100% If F.S.R. = 2.5, one can assume an efficiency of about 80% If F.S.R. = 1.5, one can assume an efficiency of about 20% If F.S.R. = 1.0, one can assume the efficiency will be 0% where efficiency of separation = f (conc. grade, %recovery)

6 Gravity Separation Devices Sedimentation Dependent: Jigs Heavy media (or Dense media – DMS or HMS) Flowing Film Methods: Sluices Reichert cones (pinched sluice) Tables Spirals Centrifugal concentrators

7 Sluices

8 Sluices

9 Sluices

10 Sluices

11 Sluices

12 Sluices

13 Sluices

14 Sluices Mean Size %Recovery (microns) 10, , ,

15 Jigs Primary stage to recover coarse liberated minerals > 2mm Feed slurry enters hutch beneath lip into slurry Moving slurry bed located above a screen Hutch fluid is subjected to a pulsating motion Upward hutch water creates dilation and compaction Pulses caused by a diaphragm or vibration of screen Separation assisted by ragging (galena, lead, magnetite, FeSi) High S.G. particles pass through ragging and screen Low SG particles discharge over hutch lip Feed size ( 1 inch to 100 mesh)

16 Jigs Floats can be tailings or concentrate depending on application (coal floats > concentrate / gold floats > tailing)

17 Jigs

18 Jigs Idealized jigging particle distribution over time

19 Jigs Idealized water flow velocities

20 Jigs

21 Jigs

22 Jigs Particle separation - conventional

23 Jigs Particle separation – saw-tooth pulse

24 Jigs Baum Jig (coal) Air used to create pulsation

25 Jigs Batac Jig (coal) Air used to create pulsation (note multiple chambers)

26 Jigs Operating variables: Hutch water flow Pulsation frequency Pulsation stroke length Ragging SG, size and shape Bed depth Screen aperture size Feed rate and density ( 20 tph / hutch at 40% solids)

27 Jigs Applications: Gold recovery in primary grinding Coal separation from ash Tin recovery (cassiterite)

28 Reichert Cone Can recover iron minerals down to 400 mesh (in theory)

29 Reichert Cone Can recover iron minerals down to 400 mesh (in theory)

30 Reichert Cone Can recover iron minerals down to 400 mesh (in theory)

31 Dense Media Separation Coal – DMS Partition Curve

32 Free Settling Ratio - DMS In the lab, we can use liquids; in the plant we use fine slurry of a heavy mineral (magnetite) 1. Consider a mixture of fine galena and fine quartz particles in water F.S.R. = [(7.5 – 1)/(2.65 – 1)] 0.5 = 1.99 So a fine galena particle will settle at the same rate as a quartz particle that is about twice as large in diameter 2. Consider coarse galena and quartz particles in a liquid with S.G. = 1.5 F.S.R. = (7.5 – 1.5)/(2.65 – 1.5) = 5.22 Note that the use of a fluid with higher density produces a much higher F.S.R. meaning separation efficiency is enhanced

33 Dense Media Separation Procedure for Laboratory DMS Liquid Separation

34 Dense Media Separation Heavy Liquids a.Tetrabromo-ethane (TBE)- S.G diluted with mineral spirits or carbon tetrachloride (S.G. 1.58) b.Bromoform - S.G diluted with carbon tetrachloride to yield fluids from c.Diiodomethane - S.G diluted with triethylorthophosphate d.Solutions of sodium polytungstate - S.G non-volatile/less toxic/lower viscosity) e.Clerici solution (thallium formate – thallium malonite) - S.G. up to 20 °C or 90 °C (very poisonous)

35 Dense Media Separation Heavy Liquid Analysis (tin ore) S.G. Weight% Cum.Assay Distribution Fraction Weight% %Sn %Cum. % Total

36 Dense Media Separation Heavy Liquid Separation (coal sink/float) S.G. Weight% Ash Cum. Floats (Clean Coal) Cum. Sinks (Residue) Fraction % Wt% %Ash Wt% %Ash Total

37 Dense Media Separation Rotating Drum DMS (50 – 200 mm)

38 Dense Media Separation Rotating Drum DMS (50 – 200 mm)

39 Dense Media Separation Drum DMS Raw Coal Capacities 1.22 m ( 4-ft) diameter drum = 45 tonnes/hr (50 tons/hr) 1.83 m ( 6-ft) diameter drum = 91 tonnes/hr (100 tons/hr) 2.44 m ( 8-ft) diameter drum = 159 tonnes/hr (175 tons/hr) 3.05 m (10-ft) diameter drum = 249 tonnes/hr (275 tons/hr) 3.66 m (12-ft) diameter drum = 363 tonnes/hr (400 tons/hr)

40 Dense Media Separation DMS Cyclone (1 – 150 mm)

41 Dense Media Separation DMS Cyclone (1 – 150 mm)

42 Dense Media Separation Magnetite Slurry Particle Size (media S.G. = 1.4) Size Cum. Wt% (microns) Passing Magnetite Consumption = 1.2 kg/t

43 Dense Media Separation DMS Mass Balance Example Wt% Assays Distribution %Solids Solids %Fe3O4 %Coal %Fe2O4 %Coal O/F U/F DMS Feed

44 Dense Media Separation DMS Separator Performance Ash in feed33.1% Ash in clean coal15.6% Ash in refuse72.0% Yield of clean coal69.0% Combustible recovery87.0% Ash rejection67.5%

45 Tables

46 Tables Particle action in a flowing film

47 Tables

48 Tabling Shaking Table

49 Tabling Shaking Table Flowsheet (note feed is classified)

50 Tabling Stacked Shaking Tables (to minimize floor space)

51 Tabling Operating variables include: Tilt angle Splitter positions Stroke length Feed rate

52 Spiral Separator Spirals

53 Spiral Separator Double Start Humphrey Spirals

54 Spiral Separator Spiral Concentrator Circuit at Quebec Cartier Mining

55 Spiral Separator Spiral Concentrator Recovery by Size at QCM

56 Spiral Separator Operating variables include: Feed rate (1 to 6 tph/spiral start depending on ore) Feed density ( %solids depending on duty) Splitter positions

57 Centrifugal concentrators Falcon (Sepro) Knelson (FD Schmidt)

58 Centrifugal concentrators Falcon C and Knelson CVD – continuous units Initial units were SB types (semi batch) Extensive use in the gold industry Falcon U/F is a batch machine spinning at extremely high speeds (up to 600G) All units exploit centrifugal force generated by spin to enhance gravity separation Apply to fine gold particles (down to 400 mesh) Slurry enters centrally and is distributed outwards at the base of the cone by centrifugal force Slurry /flows up inclined surface of bowl with high SG particles on the outside closest to the bowl surface and low SG particles on the inside which discharge over the lip at the top of the bowl. Falcon C spins generates a G force up to 200 Features a positioning valve for continuous concentrate discharge Knelson CVD operates at lower G force (up to 150G) Uses an injection water system to fluidize the bed and collect gold particles in rings Operating variables include: Spin Concentrate valve pulsing frequency and duration (Knelson) Injection water flow (Knelson) Concentrate valve position (Falcon C)

59 Centrifugal concentrators Falcon C and Knelson CVD – continuous units Applications Cyclone underflow in primary grinding circuit Flotation feed Tailings recovery Placer gold fines

60 Centrifugal concentrators Cyclone Partition Curves (GRG = Gravity Recoverable Gold)

61 Centrifugal concentrators Knelson lab unit

62 Centrifugal concentrators Knelson SB unit Knelson CVD unit

63 Centrifugal concentrators Falcon SBunit Falcon Cunit

64 End of Lecture

65 Magnetic Separation Dry High Gradient Magnetic Separator

66 Electronic Sorting

67 Filtration Filter Plate Press


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