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Laboratory Grindability Test Results and Scale-Up (6 replies)

Helena Russell
12 months ago
Helena Russell 12 months ago

A laboratory grind-ability test made in closed circuit. Should it be regarded as a miniature commercial mill operation?

It is normally not a big problem but it depends on the size of the small scale mill and the operation mode. In dry grinding we have close relation between small and large scale. We have used small lab units with 400 and 600 mm diameter and scaled it up to 3 m mills wiht good results. In both case we used air classifiers wiht similar efficiency which is critical. In wet milling, I guess it will be very much depending on your flow conditions, water concentration, efficiency of your screens or hydrocyclone etc. Therefore it will be much more difficult to control it. But if you make enough tests with differnet conditions, it will work. It is also important to use correct calculations for larger mills.

But still, should its performance be scaled- up to the size of a commercial mill?
Does the screen analysis of its product and circulating load resemble those of a commercial mill?

Tony Verdeschi
12 months ago
Tony Verdeschi 12 months ago

There's a set of efficiency factors that can be applied to the Bond ball mill work index to predict grinding power requirements in bigger plants from this test procedure.

Bob Mathias
12 months ago
Bob Mathias 12 months ago

Designing Rod and Ball mills from RWI and BWI values and using the proper efficiency factors is a well-accepted method in industry and works well for most ores (power-based calculations). Special cares to be taken for mica, asbestos bearing ore for example, and for super fine product target (under 38 microns)
Fully autogeneous grinding will require pilot testing as it is not possible to extrapolate the behavior of the large rocks from small rocks. HPGR might require testing in pilot unit as well.

Bill Fraser
12 months ago
Bill Fraser 12 months ago

Closed circuit milling at small scale (Bond mill sizes) provides opportunities to simulate mineral deportment issues, which you can't do in a basic batch mill except by doing locked cycle test, which can be a messy task for wet milling. A simple elutriator is probably the best substitute for a hydrocyclone for closed circuit laboratory milling.

12 months ago
David 12 months ago
9 months ago
Obergruppenfuhrer 9 months ago

We came across this problem in a recent project where we found that the PSD produced by batch milling in a lab scale rod mill was closer to that of a closed circuit ball mill than using a lab ball mill. This is only for simulating the effect on downstream processes such as flotation. Scale up of mills from lab scale to full scale is a different question entirely.

Marshal Dienes
9 months ago
Marshal Dienes 9 months ago

The laboratory grindability test made in little laboratory mill determine the grind ability index a determined size of the product required: 100, 150 or 200 mesh and indicates the number of grams that reach the size determined for each revolution of the mill and the parameters obtained during the laboratory grindability test is used to completed Wi (Bond Work Index). This parameter of Wi applying it in the Fred C. Bond equation we can calculate with some precision the size of the mill and the required engine power. Just as the other parameters such as the size of the balls, the classification system. But until now all mills designed in the world was used the methodology of Fred C. Bond to design their mills for the capacity required an engine power. Sometimes this parameter will be compared and shared with other methodologies ok mill laboratory test like McPherson, OutoTec. We need take care when we want to apply this parameter to design Autogenous or Semi Autogenous mill Methodology of Mcpherson it´s more adequate to calculate AG or SAG mills.

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