This document provides an overview of a reflux classifier. It consists of three main chambers - a lamella chamber at the top, a mixing chamber in the middle, and a fluidization chamber at the bottom. Feed material enters the mixing chamber where a fluidization process separates lighter and heavier particles based on density and size. Lighter particles overflow to the lamella chamber, while heavier particles sink to the underflow. The lamella chamber further separates particles using arrays of inclined plates. Finer particles overflow while coarser particles recirculate for additional separation. The fluidization chamber collects undersize material and controls discharge.

1. Knowledge Piece
On
Reflux Classifier
BY
Utsav Kant
Manager Operation (W#3)
157800
09-09-2013
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2. Introduction
A reflux classifier is a fluidised bed separator for
classifying and separating particles on the basis
of size or density .
Reflux Classifier is a combination of a fluidised
bed separator, an autogenous dense medium
separator and a lamella settler
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3. Basic Chambers of Reflux classifier
The machine consists of Lamella Chamber,
Mixing Chamber and Fluidisation Chamber
Upper Chamber is the Lamella Chamber, Middle
Chamber is the Mixing Chamber, Bottom most
chamber is the Fluidisation Chamber
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4. The Reflux classifier
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5. Mixing and Fluidisation Chambers
Reflux Classifier feed is introduced to the
Mixing Chamber via two square chutes
extending trough the lamella section. At the
base of the mixing chamber, high pressure
fluidisation water is introduced via 390
alumina ceramic nozzles and flows upwards
interacting with the slurry. The underflow is
drained from the bottom-centre of the
fluidisation chamber via an automatically
controlled underflow valve
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6. What's Inside ?
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7. Phenomena in the Mixing chamber
• The slurry inside the Reflux Classifier undergoes a sorting
process due to the force of gravity and the up flow of
fluidisation water leading to separation of high and low
density particles.
• The high density particles sink to the bottom of the
fluidised bed due to gravity and migrate towards the
central underflow valve and the low density particles are
held in the slurry suspension, which migrates to the lamella
section of the Reflux Classifier.
• The density of the middle section of the mixing chamber is
measured and used to determine when to allow some high
density solids to be discharged from the bottom of the
Reflux Classifier Fluidisation Chamber.
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8. Mixing Chamber
Coal Particles
Reject Particles
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9. Fluidisation Chamber
Water Particles
Coal Particles
Reject Particles
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10. Features of the Reflux Classifier
Fluidisation water feed valve, Fluidisation chamber pressure relief
valve, Fluidisation chamber dump valve ( Clockwise from right)
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11. Mixing Chamber - Front
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12. Mixing Chamber - Back
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13. Lamella Chamber
• Arrays of inclined plates form lamellae and divide
the chamber into zones into which particles of
predetermined size or density migrate. Particle
differentiation is controlled by plate length,
inclination and spacing in each array, combined
with fluidization rate.
• The addition of parallel inclined plates towards
the overflow section improves sedimentation
area, resulting in increased throughput compared
to conventional separators.
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14. Arrangement of Lamella Plates
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15. Lamellar boxes in Lamellar Chamber
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16. Phenomena in Lamella chamber
• The lamella channels enhance the settling rate of any
misplaced high density solids, which slide down the
plates and slowly re-circulate back into the feed zone
of the mixing chamber. This forms a slightly higher
density zone under the lamella plates.
• The low density and small particles tend to overflow
from the Reflux Classifier Lamellas in their first pass,
whereas the slightly denser and larger particles will
require the autogenous process density within the
vessel to rise to enable them to be displaced to
overflow.
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17. Inclined Plates Philosophy
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18. Lamella Classification
Water
Clean Coal
Shale
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19. Lamella chamber
• Lamella Plates made of PVC
• Lamella Plates 1.5mm thick
• Lamella box made of HDPE
• No of lamella boxes – 16
• No of feed lamella boxes – 2
• No of lamella plates per box – 79
• No of lamella plates per feed box – 32
• Lamella chamber area – 2000 mm x 2000mm
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20. Lamella Chamber (Top View)
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21. Lamella chamber
• Lamella plate spacing – 6 mm
• Over flow launder – P.U.
• Overflow Crowder – P.U.
• Overflow Launder lining – P.U
• Lamella chamber – 3180 Kg
• Crowder – P.U.
• Crowder Cover - Aluminium
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22. Flow-sheet Of Reflux Classifier
Th 1 Th 2
P. 150 P. 151 P. 148 P. 149
157 Tank
P. 157
Reflux
classifier
156 Tank
P. 155
P. 156
Tailing
Dewatering
Plant
217
218
RC U/F
Reflux
Clean coal
Stockpile
NB: 156 does not have
connection to line 1
(Dewatering plant )
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P. 154
154Tank(water)

23. Modifications
Thickener 2Thickener 1
Thickener
Head Box
Effluent Tank
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