Grinding & Classification Circuits

Grinding & Classification Circuits 2017-04-04T06:57:16+00:00
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Let the ball mill P80=150 um (constant), how can we reduce it? (5 replies and 2 comments)

8 months ago
glocmines 8 months ago

Does making the ball mill close circuit, reduce its P80. (e.g letting the hydrocyclone produce an overflow of 130 um). this would mean, most of the pulp will go to the underflow. If we do this, what is the limit for the circulating load?

The problem rooted from having the main ore (copper sulfide, Head grade= 0.4Cu) of liberation size P80=130 um, however we are given a ball mill of P80=150um. Should we install a secondary grinding? or just make it a closed circuit one? 

Alan Carter
8 months ago
Alan Carter 8 months ago

Are you saying you are in open circuit now?  Are you now in a single stage ball mill circuit? Do you have a SAG mill in front? What is your flowsheet? What is the plant tonnage? What are the dimensions of the ball mill? Motor Horsepower? Current power draw. Any ore hardness data? 

8 months ago

We are improvising a design of treating an ore with the following liberation sizes:
Cu sulfides 130 microns
Pyrite 100 microns
Magnetite 160 microns

We are given an Ballmill P80 of 150um.
we have calculated and chosen a ballmill of dimensions 7.9 x 12.8 m with 2300hp.

Its an SABC circuit. The work index of sag is 11.5 and the work index in ball mill is 8.

Alan Carter
8 months ago
Alan Carter 8 months ago

Of your 2300 HP (1700 kW) motor, how much are you drawing now? Is this already installed or are you in design?

8 months ago

we are trying to design an plant sir. the power draw is 33322 KW or
44668 hp

Alan Carter
8 months ago
Alan Carter 8 months ago

If you want help you need to learn to read and answer the questions I ask you!

Are you trying to design this with the ball mill in open circuit?

Alex Doll
8 months ago
Alex Doll 8 months ago
2 likes by Hauptsturm and David

Simplest answer: Increased specific power consumption is how you reduce the product size.  Smaller particles consume more energy.  Open circuit ball mills are not desirable for a number of reasons, and the best grinding efficiency is always achieved with high circulating loads (plan for 400%).

You have the ball mill work index, use that to calculate how much energy you need to perform the grind at each particle size.  Rowland's EF2 factor says that if you are controlling to the 80% passing size (P80), then open circuit grinding requires 1.2 times more energy than closed circuit.  This is a round number, you can do McIvor's Functional Performance calculation and get a better prediction of the performance cost of not using a classifier.

Jorge Ganoza
8 months ago
Jorge Ganoza 8 months ago

There are some aspects you should consider in your design. Your ore is very soft, it means that the non-sulphide gangue minerals would be reported in the copper rougher concentrate. For that reason, it is important to perform kinetics tests to evaluate the effect of particle size on copper recovery. The mineralogy provides information, but it is important to keep in mind the results from the flotation tests.

Other thing to analyze is the blasting parameters. The particle size distribution of the ROM material has an impact on the SAG Mill and Ball Mill performance. You have to make sure the feed size is appropriate.

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