Grinding & Classification Circuits

Grinding & Classification Circuits

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Overloaded cyclone underflow (2 replies)

Hauptsturm
6 years ago
Hauptsturm 6 years ago

How to increase the density when too much material is reporting to the cyclone underflow? Is it the right practice to increase the density when too much material is reporting to the cyclone underflow for a diamond processing plant? Cyclone pressures were a bit down but within specs, manual and instrument densities were right but still too much material reported to the recovery.

b
Robert
6 years ago
Robert 6 years ago

A few questions and comments:

  • Is this a recent occurrence or has it always been the case for this plant?
  • The separation density and efficiency in a DMC are primarily dependent on variables in list below. Have any of these changed?
  • the diameters of the cyclone and its vortex finder,
  • feed pressure,
  • the medium density,
  • the medium to ore ratio,
  • the density of the medium in the underflow, and
  • the volumetric amount of particles exiting the cyclone via the spigot and/or vortex finder. 
  • If a recent change in response, has anything changed with the plant / process or the ore being processed, e.g.,
    • Does the ore contain more clay/fines? Has PSD changed? Has a new area of the mine been opened? Has ore density characteristic changed?
    • Have the cyclones been changed or maintained recently? Has the manufacturer made any cyclone changes?
    • Has any change been made with the media?

There are two articles you might find useful:

Magwai, M, 2007 Fundamentals on the spigot capacity of dense medium cyclones

Magwei, M, 2007, Spigot capacity of dense medium cyclones, MS, Univ of Pretoria, 2007.

Chaston, I.R.M., et al., Design and operation of dense-medium cyclone plants for the recovery of diamonds in Africa, JSAIMM, vol. 75, 1975, 120-133.

https://www.saimm.co.za/Journal/v075n05p120.pdf

Regards,

(unknown)
6 years ago
(unknown) 6 years ago

I presume we are talking heavy media cyclones here? If so then you should increase the medium density to reject a higher proportion of light minerals to the overflow. But as with everything there is always a limit to what can be done effectively, as previously says increasing density too much carries the risk of increasing viscosity which impedes separation. Increasing underflow could also be caused by higher proportion of heavies in feed, and /or coarser size distribution of feed.

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