Grinding & Classification Circuits

Grinding & Classification Circuits

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Started by
I need to be able effective have a solution of handling hard ore in my SAG mill circuit. Sometimes, facing the excessive hard ores in the SAG mill is a challenge for the plants. From the operational perspective, increasing mill speed or grinding medi...
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Last commented on by ChrisCremer
Agree..Sag mill is effective upon size then must be transported by belt to ball mill for best results
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Started by
Why do ball mills have such high circulating loads?The ball mill grinds. The cyclones separate. But the pump neither grinds nor separates. So what is the purpose of having such a big pump to maintain high circulating loads in our grinding circuit?A ...
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Last commented on by margaret.aniawu
This is one of the finest explanations I have read so far. Thanks Prof
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Started by Maya Rothman
What is the best way of measuring and quantifying the grinding efficiency of mineral slurries? I am referring to determining energy savings by improving efficiency. Would the Bond Work Index be the best way?
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Last replied to by Unterstarm
Operating work indices include motor, drive and grinding mill efficiencies and inefficiencies, therefore, are not directly comparable to work indices obtained from grindability tests performed on the ...
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Started by msammet
Hi all,Please can you help me to find standards for design and sizing ball mill (calculation of thickness of shell , Ø of shell , ... ) ?best regards
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Last commented on by ABS
Hello Msammet, im also facing the same problem. do you manage to figure it out. i want to design a 3-5ton/hr ball mill for gold ore but i dont know where to start from
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Started by
Which is best for economics of grinding media do you think: High chrome steel balls and forged steel balls.I would like to know if anyone has an idea or paper on the benefits of high chromium steel balls over the forged steel balls. 
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Last replied to by banyechan
In SAG and BM,it is better to choose forged balls in wet working conditions.
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2352
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Started by Maya Rothman
Can anyone help me regarding the usage of a dry Grinding Aid & Dosing Pump for grinding of Ground Calcium Carbonate? I am planning to use grinding aid and require assistance for choosing correct aid, pump and dosage.
Last replied to by David
Hi Arif, am not if Maya is around but here is a report you may find useful https://www.911metallurgist.com/blog/grinding-aids
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I’m interested to know when sizing a new ball mill, as to why recirculating load has no effect on the power calculation, although it will have effect on volumetric capacity naturally. For instance a mill of 300tph with a 300% recirculating load wou...
Last commented on by David
look around https://www.911metallurgist.com/blog/eq
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Which power model is the most efficient to predict the correct power consumption in sag mill with change in process variables?I have developed a few dynamic simulators for different mineral/metal processing plants. Prediction of correct sag mill powe...
Last commented on by David
Do you have a grizzly ahead of you jaw crusher? What openning? Are you able to post a few photos of your working crusher? Ore pocket? Working crusher cavity? What about your coarse ore stockpile; d...
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Hello: I would like to start a new discussion. When HPGR should be used instead of SAGs in a grinding circuit. What are the technical advantages, sensitivity to feed distribution, hardness of ore, efficiency etc? What are the trade-offs between SAG v...
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Last replied to by Unterstarm
Read:http://911Metallurgist.com/C/HPGR-SAG/Compare%20HPGR%20vs%20SAG%20USING%20THE%20SMC%20TEST-TO%20PREDICT%20COMMINUTION%20CIRCUIT%20PERFORMANCE.pdf http://911Metallurgist.com/C/HPGR-SAG/USE%20OF%20...
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Started by Maya Rothman
Deseocalcular el consumo de bolas diarias para losmolinos de bolas y sag, tengo el consumo de kg de bolas /tmineral; el tonelaje de mineral a considerar para loscálculoses la cargafresca o la carga total que vamoler (esdecircargafresca + cargacircul...
Last replied to by
Tengounasimulación de nivel de llenado de bolas sag mill porsiteinteresa. Enambiente excel.
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4357
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Started by
The crop load of ball mill. It =ore + mill medium +water. But usually, it was used in a percentage formation. So how to calculate this percentage. I know this is really a basic question, but it puzzled me, for most books and papers just use it but no...
Last replied to by Paul Morrow
The ball charge and ore charge volume is a variable, subject to what is the target for that operation. The type of mill also is a factor as if it is an overflow mill (subject to the diameter of the di...
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Started by JohnnyD
The equation of the JKMRC breakage rate model published in papers is:T/hr α r.s.(1-a)There is no =How should I read and understand this rock breakage rate equation?
Last replied to by David
The 'equation' is a first-order rate relationship. The 'α' is a 'proportional to' symbol ( more correctly depicted as ∝)Throughput (T/hr) is proportional to r.s.(1-a) where, r = breakage rate, s = ...
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Started by Jean Rasczak
Does the choice of regrind mill and mill media affect downstream flotation performance? As it relates to http://www.sciencedirect.com/science/article/pii/S089268751400140XUntil recently little attention has been paid to the effect of size on flotatio...
Last replied to by
Why in the tails of the plant is 25% copper as chalcocite? And can be this copper flotation at low pH in the presence of xanthate? And flotation is carried in pachucs? If so, then:1. Apparently the ch...
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Started by
Am looking for the most or best Wear Resistant Mill Liners and manufacturers. Please could you advise what your recommendations for the best possible liners to use in an Iron Ore application and please share what %Mn was used including the % Cr if us...
Last replied to by
and if you are feeling rich http://www.magotteaux.com/
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Started by
Can people say that either they are happy that they selected sag mills or say they made wrong selection. In either case, if examples and a bit of information on ore type/top size/hardness of the ore/power consumption.
Last replied to by Zander Barcalow
This is good too http://is.gd/TJWe5O
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Started by Marshal Meru
Having used weight control and power draw to control Mill operations, using Mill Sound to run a mill was a new one for me. I found it unusual and not that effective.Has anyone else used that style of operation control to run their mill and did you fi...
Last replied to by
Mill Ears - that brings back memories. Love them. But my favourite was the initial work in South Africa with "Instrumented Liner Bolts" (Kloof Gold Mine SA, Mintek) measuring impact and conductivity (...
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Started by
How to define Quality of Grinding Media? Grinding media used in SAG Mills are subjected to strong abrasion and impact. They lose mass both in a continuous microscopic abrasive process and through discrete fracture of pieces that may range from a thin...
Last replied to by
Many of our customers write their own specification for ball chemistry and physical characteristics. Some also test every batch to ensure compliance with what specification is ordered. Getting what yo...
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Started by
Is the air core formation inside a hydrocyclone is needed or not? Got confused as many research papers suggest to minimize the air core diameter by several design modifications within the hydrocyclone. On the contrary air core is necessary to carry t...
Last replied to by
Some few fundamentals all know about cyclone.Air core:This will become Zerto in ropy underflow. In Ropy under flow few coarse particles which are supposed to come out from under flow, will try to esca...
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Started by
How do I size and design a mill for magnetite ore types with 75-250 t/h working? The ore consists of about 30% quartz and 30% magnetite and the amount of hematite is lesser than magnetite. The liberation of magnetite is interlocked with other mineral...
Last commented on by Zander Barcalow
Your production capacity seems to be low (max. 250 t/h). I do not know the required magnetite liberation size and weight recovery level. Based on the power consumption criteria, the best grinding flow...
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Started by Zander Barcalow
How much of an effect, if any, does rheology inside a SAG mill or any grinding mill? Does it have an effect on residence time?
Last replied to by
I have seen a ball mill circuit where a cyclone cluster (instead of a thickener) was employed for dewatering of the mill product stream upstream from gold leaching, and the cyclone overflow stream (i....
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925
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Started by
Looking at dry grinding material of extreme hardness holding a BWi of 27kWh/t from an F80 of 6-8mm to a P80 of 16um in an air-swept compartmented ball mill. There are operating plants doing this to 75um, is 16um too fine? Only considering milling tec...
Last replied to by Zander Barcalow
If you expect to keep the dry process, as mentioned, the BM F80 is «coarse» under incidence of the required P80, and you are obliged to help the BMs. You can think to the HPRG equipment or study the...
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Started by
Please what is the best way of measuring the dosage of a semi-solid, solid, and liquid chemical grinding aid during wet grinding?Is it not possible to have a grinding aid (to be used for wet grinding of an ore) in solid form?My interest is on batch ...
Last replied to by Jean Rasczak
It's really about where the circuit operating conditions lie with respect on a curve of % solids - viscosity - grinding efficiency / cyclone efficiency. Truly the answer will be found through experime...
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Started by PERTHIAS
A SAG mill operates with a 10000 hp motor. Typical power draw is 80% of maximum. The 80% passing feed size to the mill is 5 inches and the mill discharge has an 80% passing size of 2.1mm. How do i calculate the Operating Work Index for this mil...
Last replied to by David
Try this SAG Mill Operating Work Index Calculator http://www.911metallurgist.com/blog/formula-to-calculate-a-mill-operating-work-index-equationIt looks like 6.6 kWh/ton
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Started by Maya Rothman
Electricity is one of the industry’s main cost drivers: higher energy costs will force closure of mine shafts.The key is to improve energy productivity, regardless of the source, starting with best practice operations. CEEC is supporting the global...
Last replied to by
A very accurate assessment. The driving force will be the cost of energy.
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Started by
If crop load =ore + grinding mill media +waterBut usually, it was used in a percentage formation. So how to calculate this percentage.I hear that generally 40% of mill volume is used by media and 60% of it (media volume) is solid , 40% is void.I ...
Last replied to by
I have to disagree with you... it is not "cast in concrete".Depends on the ore and mill type and for what goal or purpose.. What if it is a dry milling operation? Sag mills in the gold and copper ope...
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Started by Bob Mathias
What will be the better option in a Ball Mill Grinding Circuit: Screening or Cycloning?The separation is 500 micron and the feed is 100 TPH
Last replied to by
Yes the capacities need to be considered, but also the percent solids being feed to the system. With recent trends being to feed cyclones at high solids, there separating efficency is decreased, As t...
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Started by
Anyone has experience for TBS (teetered bed separators)?  I would like to know how much is the feed solid% and which size fraction is working better than spiral?
Last replied to by
Thanks to you all. i want to use this machine for coal for size range of 0.3 mm up to 3 mm. you mentioned good points.I found useful http://www.saimm.co.za/Journal/v102n07p385.pdf
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Started by Maya Rothman
Hydrocyclones sort particles by weight, hence if mineral of interest is dense it will tend to create slimes/fines (say -10 or -20 mm). Would screens prevent this? Any case study of screen technology the work well enough to provide a fine product of i...
Last replied to by
Separation efficiency of cyclones depend on how the cyclones are operated and controlled. This means first selecting correct gear for the specific application. Then decide on the operating / control p...
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What is the optimum/possible ash product size P80 that be obtained a comminution operation using rotary breaker in coal preparation ? What modifications can I make to improve ash reduction?
Last replied to by Victor Bergman
I would suggest you aim to increase the 'open area' of the breaker. This is the proportion or quantity of holes relative to the total surface area. This may impose structural constraints, but ultimate...
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Started by
For me it is interesting to see a lot of discussion around the topic of reducing costs for grinding, but very little comment or effort apparently being put into understanding the requirements of the grinding in the first stage. The question of why ar...
Last replied to by Victor Bergman
We have put a great deal of time into secondary grinding by gaining much better control of the forming of a small ball population. Having the media remain round (Spherical) during deployment life is n...
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Started by Helena Russell
Is it advisable to use a SAG mill for small, say 2000 TPD concentrator operations? The processing, in this case, is a complex zinc/tin mineral and we are afraid a SAG would P80 produces too much fines (since the tin is to soft brittles) (tin cassite...
Last replied to by Helena Russell
Thanks to veryone. I agreed that SAG is not the best option in our case. So still evaluate some alternatives. Also Gekko, on this application is not optimum.Thanks again for your help.
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Are the old Allis-Chalmers Abrasion Index and calculations for Steel Balls and liners consumption still valid?  The Allis-Chalmers Standard Abrasion test has been used for several decades to calculate steel consumption. Current advances in alloys ...
Last replied to by
I think you have made a point here: the grinding circuit needs to be under control before someone tries to assess steel balls consumption. "Under control" means that operators in each shift operate us...
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Started by Victor Bergman
For a conversion of mill lining from polymet to steel; What effects will there be on power draw, grinding or other operating/performance variables? I am looking at the possibility of converting a steel/rubber hybrid AKA Polymet lined SAG mill to ste...
Last replied to by David
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I'm faced with contradictory claims concerning classifying liner regarding their effectiveness, energy efficiency or applicability for high tonnage or hard/abrasive ores. Litterature is really scarce on this subject. Classifying liners are a kind of...
Last replied to by David
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Started by
I would like to know the relationship between mill weight and mill liner wear, is there an existing model for this? Has anyone looked at this before? Obviously low mill weight can impact toe position, reduce attrition and abrasion breakage, increase...
Last replied to by
Scanalyse (now Outotec) are investigating these type of relationships by integrating precise liner wear and volume measurements with mill operating parameters, including mill weight. One the Analytica...

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