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Modification of production throughput of ball mill (4 replies and 4 comments)
Suggest that as a first step you run some simulation on the effect of decreasing your F100 from 20mm to say 15 or 12mm.
Thanks for the reply. We used to decrease F100 to 16 mm and yes we reached 53 t/h but it doubled crushing costs! So modifying mill parameters such as ball filling and solid concentration is our first priority.
More tonnes means you need to draw more power. Use the power models as your guide. For example, the H-F model predicts that:
- P ∝ D^2.5, so can you use a thinner liner to give you a greater effective diameter?
- P ∝ L, so can you make the chambers longer?
- P ∝ Nc, so can you increase the speed (change a pinion to one with fewer teeth)?
- P ∝ ρ, so can you increase the apparent density (denser balls, less water)?
- P = f(J, Nc), so more filling might give you more power or it might not, depends on the speed you are running and your liner configuration. Your 45% is probably too high depending on the speed you are running.
Knowing the filling level that gives you the maximum power requires some trial and error, and will probably be something you simulate using the models. All models assume you have "efficient liners" that provide adequate lift to the material -- do you? If the shell is smooth, put a wave liner on it.
Also consider that the circulating load should be as high as you can tolerate because more frequent passes at a lower retention time in the mill gives more efficient grinding.
Thanks for the reply Dear Alex.
1st chamber liner type is single wave and 2nd & 3rd chamber liner type is double wave which seems efficient and mill speed is 75.2% of Cs.
What is your suggestion to increase circulating load except adding water and upgrading intermediate diaphragms?
We can not change the speed and the length of chambers but density can be changed.
Models predict more power can be drawn by increasing ball filling (which is currently maximum 30%) but I guess it may cause mill overfilling & jamming (which we have experienced when feed BWI had increased to more than 22 kWH/t) as charge (ball + slurry) filling is currently about 45%.
I'm not sure if drawing more power by adding more grinding media can increase throughput by itself unless we decrease charge filling by increasing slurry density. I look forward for your help.
Best regards
Considering energy cost, crushing operation should be done to the minimum size as possible. Since load on ball mill will be more now, there will be more power requirement to do the same size reduction. Its better to have an integrated approach to the problem of crushing and grinding with necessary changes to minimise energy cost. you may review overal effect of both crushing and grinding with crushing down to say 15 mm to take a decesion.
Dear dk,
We used to crush down top size to 16 mm before but it doubled the crushing costs. That's why we are trying to increase throughput by modifying mill operating parameters such as ball filling %. With more tonnes there will be more power requirement to do the same size reduction but it will also let us to send one of 3 ball mills as a standby. So energy cost seems to remain unchanged.
The only reason why there is no significant power increase is probably due to a coarser discharge. As DK said one needs to look at all aspects of the power equations. Adding multiple ball sizes only creates a logistics problem as balls wear they fill the intermediate size ranges, before being passed to the next stage. A P80 of 63micron is not very descriptive as it does not fully describe the shape of the discharge grind profile.
There are 3 ball mills in our plant so we should differentiate between ball mill power and total power of ball mills which is sum of each ball mills power. By increasing throughput the mill power will increase too but it will also let us to send one of ball mills as a standby so total power seems to remain unchanged.
The question is how to increase ball mills throughput? We are thinking about increasing ball filling from 30% to 40% but overfilling is concerning us because current ball + slurry filling is high (45%).
Hello Dear Friends,
We are working in a plant with single stage grinding using three parallel wet three compartment ball mill. Each ball mill operates in a close circuit with Classifier. The fineness of ball mill product is OK so the circulating load is insignificant (44 Kg/h). The overall data of each ball mill circuit are following:
Power calculations were done by some models including Bond, H-F, Morell & ...
We want to increase the Throughput to about 53 t/h while maintaining P80=63 micron. How capacity can be maximized? Power calculations showed that we can increase ball filling to 40%. as mentioned before ball + slurry filling is high so we may consider increasing ball filling to 40% and solid concentration to 55% at the same time to prevent ball mill from overfilling and jamming. Is this the right choice to increase the ball mill throughput without upgrading the intermediate diaphragms?
Any help would be appreciated. Thank you for consideration.
Best Regards