FLOWING FILMS CONCENTRATION | TABLING | DMS

Flowing Flim Concentration


Fluid flow can be classified in to
1. Laminar flow or streamline flow
2. Turbulent flow or erratic flow
3. Mixed flow : A combination or laminar and turburnace flow.

● Liquid films under lamir flow have specific mechanical property that can be easily adopted to separate the mineral. The specifics mechanical property is that, the velocity of the fluid is not the same at all depth of the film.

● In case of pipe, the flow is maximum along the central axis and nil at the linear periphery of the pipe. This properties in turn depends upon the viscosity of the fluid.

● This physical sence of the path difference during fluid flow at different depth can be exploited industrially to result in mineral concentration.

● Flowing film concentration can be as follows
1. Fine heavy particles
2. Coarse heavy and fine light
3. Coarse light particles.

● In fact rounded particles move farther down stream than the heavier, Finer and flatter particles. It is interesting to note to note that flowing film concentrate places the coarse heavy particles with fine light particles.

Tabling

The  shaking or Willey travel consist of a substantially plane surface (the deck) in inclined slightly from the horizontal and shaken with an asymmetrical motion in the direction of the long axis. Asymmetrical motion means, the stroke of the table is faster in one direection.
Wilfey Tabling separation
Wilfey tabling process

● Usually the back stroke is faster compared to forward Stoke.
● The wash water flows over the table at right angles to the direction of jig.
● Longitudinal deals or riffles are fixed on the table surface in the direction of the table movement.

● The lighter gangue material are thrown in to suspension and are discharged over the edge of the table opposite the feed box by the wash water.
● The havier minerals finally arrange themselves on the smooth unfilled proportion of the table.
● When they encountries the full force of the wash water.
● The middlings are selected in that corner of the table which is intermediate between conertrate and tailing.

Characteristics of Shaking Table Operation:

● Under idealized condition particles separate in to four groups.
1.Light -large
2. Large-heavy
3. Small- light
4. small- heavy

● The angle of inclination of shaking table depends in the mineral handled
1. Size of the feed
2.Wheather the operation is cleaning.
3.The difference in specific gravity between the mineral are to be to departed.
4. Avg. specific gravity of the minerals to the treated.

● Capacity of Wilgley table
    The table size of 4ft×2ft has capacity as high as 200 tons/24 hours.

● Cost of operation
 1. Power 0.5 - 0.8 kW/hr
 2. Repairing cost of seats and deck as and when required.

Use of wilfley table: 

1. 20 conuntrate cossiterite.
2. 20 conutrate free milled gold ores.
3. Beneficiaries non- metallics like glass and sand etc.
4. For cleaning fine coal.
5. As a pilot and guide to flotation plants.

Dense Media Separation (DNS/HMS) 

Dense Media Separation(DMS) in other terms what is called as Heavy Media Separation (HMS).In this process Heavy liquids of suitable density are used, so that lighter density mineral naturally float and, while those denser than it sink. 
Dense media - heavy media separation
Dense or heavy media separation 

● In such a way this DMS process also called as sink-float process. Dense Medium Separation is a well known Technique for separating particulate solids of different densities in a mixture. In simple terms it is a suspension of dense particles in a liquid. 

● The Mixture of particles for separation is mixed with suspension, and the different particles allowed to Sink or Float. It is the simplest of all the gravity process in principle wise and it is considered as Standard Laboratory method for separating minerals of different Specific gravity

● In DMS we can separate material at any required density, with a high degree of efficiency even of the Near -Density material. The density separation can be closely controlled with in a relative density of ±0.005 kg/l and can be maintained, under normal conditions, for indefinite periods. 

● The separating density can, however, be changed at will and fairly quickly, to meet varying requirements. Dense medium separation is applicable to any ore in which, after a suitable degree of liberation by crushing. This process is most widely applied when the density difference occurs at a coarse particle size, as separation efficiency decreases with size due to the slower rate of settling of the particles. 

● Case separation can be effective when the particles diameter is more than 4mm in diameter, and the difference in specific gravity is 0.1 or less. Separation down to 500 microns, and less, can be made by the use of centrifugal separators. 

Wemco cone separator : 

● It has relatively high sinks capacity and widely used for ore treatment. It can accommodate feed size up to 10cm as the size of the cone diameter is around 6mts, with capacities up to 500 t/h. By free fall the feed is introduced on the surface of the medium to plunge several centimeters in to the medium. The rakes which are mounted on the central shaft keeps the medium in suspension by gentle agitation. The float removed by over flow while the sink by a pump or internal air lift.

Drum separators : 

● Drum separators are built on several sizes, up to 4.3 m diameter by 6 m long, with maximum capacities of 450 t/h and can treat feed up to 30cm in diameter. Removal of the sink product carried out by lifters which are fixed to the inside of the rotating Drum. The lifters empty into the sink launder when they pass the horizontal position. The float product overflows at the opposite end of the drum from the feed chute.
Drum separator
By the action of revolving lifters longitudinal partitions separate the float from the sink. When compare with the cone separator it minimizes settling of the medium particles and giving a uniform gravity throughout the drum. 

Magnetic drum separator
Magnetic Drum separator

Two stage separation is required when single stage dense medium is not giving desired recovery. In this situation, two- compartment drum separators are mounted integrally to make one feeding to the other. In such a manner, the lighter medium in the first compartment separates float and the sink product is lifted to second compartment. These are very useful in the coal industries because of their simplicity, reliability and relatively small maintenance needs. 

Dense medium separation advantages: 

  1. Reduces size of milling circuit.
  2. Saves capital operating costs and energy consumption.
  3. Applicable to any ore after a suitable degree of liberation by crushing.
  4. It has the ability to make sharp separations at any required density, with a high degree of efficiency even in the presence of high percentage.

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