Crushing, Screening & Conveying

Crushing, Screening & Conveying2017-04-04T06:57:13-04:00
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Reducing top size with minimum fines (6 replies and 4 comments)

2 years ago
Smuts 2 years ago

We are producing crushed dolomite with a top size of 3mm using a HSI crusher and want to reduce the top size to 1mm while not substantially increasing the -300 micron fines. Current raw feed is 19mm stone.

Is it possible to do this? If so what kind of adjustments will have to be made to the crushers or are other crushers like a rock on rock VSI be more appropriate for the change?

My biggest concern is that just changing the screens to 1mm will cause a lot more fines to be produced, while we already want to reduce them if possible. I know my ideal situation is asking for a bit much, but any information about either which crushers will perform better or how I can change the current setup to decrease my top size and fines would be greatly appreciated.

Master Q
2 years ago
Master Q 2 years ago

What sort of throughput are you looking at ?

What % -300 microns do you consider excessive or acceptable?

2 years ago

I am unsure exactly what the current throughput is but I expect it is around 60 t/h. We are also not running at capacity, so we could increase running hours to ensure we meet the demand, so longer run time could be acceptable.

We have a limit on -100 microns, which is 10%, but our thinking is that we won't be able to effectively screen to that size.

2 years ago

Sorry I realize I did not mention it in my question:
We already producing on the limit of the fines our client finds acceptable. So reducing the top size would put the fines fraction past specification. We want to switch the feed of a ball mill over to the fines removed (the -300 microns), but if there is too large of an increase in the fines produced we will exceed the ball mill capacity.

2 years ago
BAUD 2 years ago

If you do not get it in one shot, try the following:

-Screen to 1mm  and keep minus 1mm as final product

-Grind the plus 1mm (- 3 mm + 1 mm) in a ball mill ( lab test first) and assess

Peter J
2 years ago

If you already have an existing oversize protection screen on your vibrating screen you should have a fairly good idea of what your oversize fraction is. To reduce fines simply increase the mill feed rate, returning oversize will help but you may also need to increase the new feed rate (or increase size of mill feed by increasing the feed rate to the VSI)

2 years ago
dk 2 years ago

You may try to screen out at 1 mm and +1mm may be recirculated back to crusher with lower capacity crusher as its runing now and with longer operating hours if its possible. For trial run start with different capacity at 1 mm dry screening to optimise the pant capacity. If required another crusher may be required after necessary studies.

2 years ago
Turgay 2 years ago
1 like by Smuts

If you want to buy a material between 1 mm and 300 microns,
It is appropriate to use a high-pressure roller crusher, at least the fine grinding may be the end result.
You must leave the gap between the rolls open at 800 microns
You can buy the product between the grinding scale.

2 years ago

Yes! That seems like a very good solution to use a roller crusher, it will decrease the top size and reduce the fines. I will look into doing some tests to see if our dolomite is not too flaky.
I haven't worked with a roller crusher before, how much more maintenance and operating costs does it have relative to other crushers like a VSI?

2 years ago
JoziBoi 2 years ago

Hi Smuts.

With regards to your HSI, can you let us know what kind it is?


How many rows of blow bars?

Is it a vertical inlet?

What is your rotor speed?.



Alex Doll
2 years ago
Alex Doll 2 years ago
1 like by David

Remove the balls from the ball mill and install rods instead.  Rod milling makes significantly less fines and can function down to 100 µm as long as the reduction ratio is not too great.

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