Ball Mill: Most Efficient Process?

Blurb...

http://answers.yahoo.com/question/index?qid=20080331213041AAtJkme

Hi SolarEagle! before posting my question I searched the Internet, but besides the description of the mill, no useful info showed up. I will see if the formulas on your link match our findings.

Perry's Chemical Engineers' Handbook, 5th Ed. has a section 'Size Reduction and Size Enlargement' which gives the principles and an overview of different kinds of size reduction.

Also Taggart's 'Handbook of Mineral Dressing' - has a good section on ball mills.

The only way to predict the efficiency of the process is to carry out pilot-scale trials.

I agree

empirical information....... also since the op said that testing was done a long time ago....... see what information or data was collected.......... if any.

I agree with PWS, everything that I found on the web matches my experience of running tests varying the feedstock size, ball size, and dwell time.

Since you didn't mention feedstock some of these papers may not be applicable to your situation.

http://www.saimm.co.za/Journal/v072n11p277.pdf

http://www.mine-engineer.com/mining/ballmill.htm

http://uu.diva-portal.org/smash/get/diva2:545605/FULLTEXT01.pdf

and here

I also agree. Add a little witchcraft and you might be in the ball park of where you want to be. Had one ball mill process where it seemed that only one operator could do it efficiently and right on the middle of the spec range. He once borrowed my hard hat because his fell into bad stuff. That batch was done in less time, right on spec, right particle size and best batch run in several years. He swore it was the hard hat. I didn't argue with him, I got another one. Always had one that had been worn by me ready for him in my office. He swore all batches were better from that point on. Always made sure we were overstocked when he went on vacations.

Good Luck, Old Salt

Your comment tells the issues we have to deal with every single day! There are 4 guys in different shifts who mill small batches (100 kg) of an acrylic polymer. One (operator A) gets perfect results, and the other 3 (operators B, C, D) get variable results. All swear they follow the procedure step by step. We always try that one (B, C, or D) shares the shift with A. Quite often we have to blend batches made by different operators in order to meet specs. Unfortunately your comment confirms my hunch and worst fears: we are in the hands of SIBBMO so it is plausible to think the problem has no solution! Regards!

Oh, almost forgot: SIBBMO stands for "Secret International Brotherhood of Ball Mill Operators"

I don't know hat the meaning of SIBBMO is.

But you found your answer. document the procedure from your best operator.

And also look at your other operators that isn't performing. That is the problem issue.

"I don't know hat the meaning of SIBBMO is": please read the last sentence of the previous post!

Operator "A" has learned the procedure from the Production Method for the product. This document is reviewed every time we notice a deviation from mean results. Operator "A" participates in the revision.

ha....... thanks..... how did I miss that?

^{Secret International Brotherhood of Ball Mill Operators - Local 317}

Now you´ve got me: what stands Local 317 for?

Due to the time (and $) wasted blending out-of-spec materials with product which was made to be at the other end of the spec range we did an extensive study of the problem. This was done by assigning supervisors to be the "helper" for all batches of this material. Even went so far as to vcr tape batches for a while. No significant difference between the operators was found. Also had a supervisor make a batch once. That was way, way out of spec.

Finally had the "consistently good producer" retrain the others. At the start of this it was not well received by some of them because to good guy was the youngest (about 1/2 the age of the others) and had the shortest tenure with the company. Result- still had same differences between operators.

The process was finally moved to the other coast due to the relocation of the customer. A very happy day for me and others.

Good Luck, Old Salt

Ha, you see! SIBBMO striked once again! They finally managed to divert the production to "the other" coast. No matter where a plant is located, SIBBMO always wants to do their secret operations somewhere else!

I worked in the tumbling dept at a ball bearing plant a long time ago.

Everything was dependent on the size/material of the balls. We started off with emery, finished off with lime, and washed with caustic soda.

There wasn't really a set standard...it was more of a zen thing. We would mic the ball bearings every hour or so to start (maybe less), then when they got close to correct size, we would check more often; sometimes as often as every 1/2 hour.

Letting them go too long, and getting them too small, was a really big deal with management. It could get you fired.

Cancel that last post. Wrong thing.

I've heard that crystal balls work well for this. (predicting, that is)

Too many variables in my book. Feed stock size/hardness/how abrasive, etc.

As the size of the feedstock is reduced the grinding rate varies also. And the list goes on, and on.

Trial and error is how I'd approach it.

Efficiency of mill, how do you define it! Power consumption and ball charge consumption are more relevant. In ball mill the power consumption is required for rotation of ball charge and mills. To reduce ball charge and power consumption mill should be run at full load.

If you plan to replace the mill the same factors should be considered. Formulae may not help you.

there are a lot of variables, OP should make a list on the conditions and what the actual goal is.

And try to tie things down so its not so open ended.

"To reduce ball charge and power consumption mill should be run at full load"

Sorry to disagree, but "running a mill at full load will decrease the efficiency of the process, as balls cannot gain the necessary momentum for crushing the substratum.

When I said full load I mean runiing the mill at its rated capacity not filling the mill fully. The ball mill uses impact and artrition for grinding. Impact is caused by the falling of ball charge from a height which will happen when mill has some free space.

I was at IOC in Wabush years ago and they used the ball mill to crush iron ore. I asked the same question and was told it was an old proven design and they adjusted the rpm till they got the correct powered crush.

The unit was around 15 feet in diameter and turned around 30 rpm. The balls were carbide and around 12" diameter. Played hell with the weldments on both ends which is why my mentor and i were there, to find an automated method for ultrasonic inspection.