Grinding & Classification Circuits

Grinding & Classification Circuits 2017-04-04T06:57:16+00:00
  • To participate in the 911Metallurgist Forums, be sure to JOINLOGIN
  • Use Add New Topic to ask a New Question/Discussion about Grinding.
  • OR Select a Topic that Interests you.
  • Use Add Reply = to Reply/Participate in a Topic/Discussion (most frequent).
    Using Add Reply allows you to Attach Images or PDF files and provide a more complete input.
  • Use Add Comment = to comment on someone else’s Reply in an already active Topic/Discussion.

SAG Mill Slurry Rheology (5 replies)

Zander Barcalow
2 years ago
Zander Barcalow 2 years ago

How much of an effect, if any, does rheology inside a SAG mill or any grinding mill? Does it have an effect on residence time?

Ace Levy
2 years ago
Ace Levy 2 years ago

Rheology can play an important part in residence time in a mill. Trying to classify a thixotropic slurry is most difficult since the particles are no longer acting as 'individuals' but rather as a mass that entraps the fine particles, preventing them from moving on to the next stage.

Sugar Watkins
2 years ago
Sugar Watkins 2 years ago

Why not re-phrase your question a bit more clearly. Are you trying to push the density to such a limit that you are grinding a paste which essentially means that you are no longer grinding! It would seem obvious that grinding in this condition is no longer grinding. Maybe your question is more how far can you push the density and still achieve acceptable performance. Note that this viscosity that you refer to may in fact change from day to day as a function of feed material such as clays.

Dizzy Flores
2 years ago
Dizzy Flores 2 years ago

You have a good point in re-phrasing your question. Certainly, as the ore mineralogy changes, so will the viscosity. Adding more water can help if the viscosity is high but then your mill capacity will decrease. There is always a price to pay when changes are made to a process circuit.

Zander Barcalow
2 years ago
Zander Barcalow 2 years ago

Ore characterisation is core to my work and one of the 'great unknowns' is what role mineralogy plays and what to extent, it is all part of the scope so thanks. You make a good point with regard to viscosity/density, I do need to address the question of limits to which densities may be pushed especially when dealing with ores that have a tendency to assume a paste-like consistency when ground.

Carmen Ibanz
2 years ago
Carmen Ibanz 2 years ago

I have seen a ball mill circuit where a cyclone cluster (instead of a thickener) was employed for dewatering of the mill product stream upstream from gold leaching, and the cyclone overflow stream (i.e. water with a low % ultra-fines) was used as mill dilution. Needless to say, a few months down the line the mill started showing serious throughput capacity problems, and this was due to a build-up of ultra-fines in the mill circuit over time i.e. the pulp rheology had gone toxic. The pulp inside the mill was so viscous, I could walk on it (my feet did not make much of an impression on the pulp surface).

So yes, maintaining proper pulp rheology (the combination of pulp SG and viscosity) in the mill is extremely important. However, if the ore characteristics dictate otherwise (such as a high clay content in the ore), it may be best to scrub & classify the ore upstream from passing the coarse size fraction to the mill.

Please join and login to participate and leave a comment.

BUY Laboratory & Small Plant Process Equipment

We have all the laboratory and plant equipment you need to test or build/operate your plant.

ENTER our Mining Equipment' Store

We Sell EQUIPMENT for all types of Mineral Treatment PROCESSES and Laboratory Testing needs

Have a Mineral Processing QUESTION?

Come in, ask your question

911Metallurgist Community Forums

Talk to other metallurgists and be helped.


We can IMPROVE ALL PLANTS / Mineral Processing Engineering & LABORATORY Ore Testing

911Metallurgy Engineering

Contact us for process engineering, metallurgical investigations, plant optimization, plant troubleshooting, needs. WE “FIX” METALLURGY.