Grinding & Classification Circuits

Grinding & Classification Circuits

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Started by Vinzo 3111
the derivation of the formular of ball load from basic principles
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Last replied to by Jorge
Follow the link below, https://www.911metallurgist.com/blog/ball-mill-charge-volume-calculation
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Started by Ceverett
Just wondering if anyone has a ball or SAG mill with a trunnion magnet to remove scat steel and if they are willing to share the results. Looking into getting one for our SAG mill but looking for proof that it actually creates power savings, ball con...
Last replied to by SmartDog
Trunnion magnets will work, unless you are using steel balls or grinding a magnetic ore.  Since the magnet will pickup magnetic material, they will pickup scats (ball pieces and chips) and balls that...
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Started by Pommy35
Hi folks.  we seem to have s bit of a debate on my plant. When grinding out your ball mill, if the mill power draw (KWS) struggle to rise above lets say in this instance 2180kws but you are hoping to achieve 2250kws. Does this indicate the mill is ...
Last replied to by SmartDog
Power draw is based on total load, charge plus feed, and then grindability.  If the feed is achieving the proper grind size with a lower power draw it could be that you are under feeding and/or the g...
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Started by Ceverett
In our grinding circuit, we have a SAG mill that uses rubber liners. Once the liners are worn out and replaced we sell the old liners to a company for a credit where I am guessing they either burn them or leach them in a tank to recover the gold embe...
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Last replied to by AAFilipe
Honestly, this is not a thing that you should be worried about. The gold content on liners won't make that difference to you, while to recover it you would have to invest in an equipment that is not ...
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Started by Dewald
Hi. can someone assist me with a few problems I have? We have a overflow dry grinding ball mill grated discharge 2.4m x 1.5m, we use 40mm,25mm and 17mm ball sizes (high chrome steel) to mill manganese with a top size of 4800um, mill liners are stee...
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Last replied to by Dewald
Sorry mill is 2m x 3.4m
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328
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Started by Sam_123
Hi everybody, I want to calculate the mass moment of inertia of ballmill inorder to correctly size my motor & to calculate the starting time of motor.could someone help me. Thanks
Last commented on by SmartDog
This is multi term integral based on a specific mill configuration. You would need to develope this for your mill based on the mill drawings, assumed charge and momentary feed rate. There is no gene...
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314
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Started by SDG
Hi Everyone,  I am interested to have your opinion on dry grinding/ air classifier circuits. Specifically, how would you approach mass balancing on the following attached exmaple using a 2 air classifiers with a mill/ HPGR placed in between (a simp...
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Last replied to by SDG
Hi again everyone, sorry there was a mistake on the block diagram before. The correct one is attached herwith. Thanks for your opinions and cheers!
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798
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Started by akfury
Running this dirt in any gravity separation I've tried induces packing/plugging and gold loss. All kinds of sluice setups & centrifuge. Centrifuge struggles and is too little production. Looking at Hydrocyclone for results? Problem areas are mainly 3...
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Last replied to by Jorge
It is important to perform a testing program based on information from a mineralogical study. Probably, it would be necessary to consider two concentration stages to get an acceptable concentrate grad...
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428
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Started by Gallo
equation to calculate the mill weight using mill charge level and load cells
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Last replied to by Jorge
Nowadays, probably, the best systema to measure the load is to install load cells. It is necessary to indicate that the load cells are calibrated to measure the total weight of water, steel balls and ...
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388
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Started by Ceverett
We have a problem with scat steel buildup in our gold gravity circuit and are looking at solutions to remove it for a steel buyback program. One of the ideas discussed was getting a new screen installed for our cyclone underflow and installing a belt...
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Last replied to by ManUtd67
From a metal recovery perspective a good idea as metal is well presented to the magnet.  Issue is any steel will become magnetic.  Have done this before with stainless on the discharge of the screen...
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375
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Started by Fuloshixwa
I am failing to measure my DMS vortex finder length during maintenance day because it quite difficult to access from the spigot end. Any suggestions guys?
Last replied to by SmartDog
For most cyclones the overflow discharge is bolted to the outlet which is the vortex finder.  Removing the overflow pipe you can easily measure the diameter and then reaching inside you can measure t...
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416
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Started by evandewitt
Our wet Ball Mill griding media reject (scats) from the trommel screen is an odd shape ( see photo attached). I’m not use to this wear shape of grinding media in a ball mill. Normal wear of grinding media in my experience is down from a spherical t...
Last replied to by David
And what is your question exactly? octagon/nonagon shapes ball leftovers are the result of a soft inner core - 55 to 59 Brinell. spherical to a non-spherical (egg shape) will result from a harder co...
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381
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Started by Steve
We recently converted our metso 18X11 steel lined Rodmill to rubber lined trommel discharge Ballmill to improve grinding efficiency and increase throughput. Our rodmill used to run 120 tons/hr at a critical speed of 61.5% with rods diameter of 3".  ...
Last replied to by SmartDog
There are many factors that impact on mill sizing and performance that you do not mention, particular grindability, desired product size, open or closed circuit, wet or dry grinding, what material you...
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Started by Fuloshixwa
I am sizing a cyclone for slime removal for a new plant but I am struggling to determine ideal operating conditions such as feed velocity, feed pressure and pulp density. I am thus looking for article referrals. Or sites where I can download them for...
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Last replied to by jbessett
I was wondering if someone could explain the input parameters for https://www.911metallurgist.com/blog/hydrocyclone-design-equations-and-sizing-parameters-calculations ? Or perhaps the design equatio...
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474
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Started by Metals Guy
Does anyone know of any plant operating with an automated Single stage SAG milling circuit most preferably in Africa. If there is anywhere else besides Africa be free to tell.  
Last replied to by David
Does the SAG mill know it is located in Africa? I have to ask because the laws of physics in Africa are not the same as the rest of the world... So, seriously Metals Guy tell us why Africa is so im...
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453
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Started by Fuloshixwa
How do I do material balance on an open classification circuit with a cyclone as a classifier. It is a desliming cyclone with the underflow as my concentrate and the overflow going to the tailings dam. Any piece of literature out there I can consult....
Last replied to by SmartDog
Regardless of the equipment type, material balances are calculated the same.  See: https://www.911metallurgist.com/blog/metallurgical-accounting-formulas  
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797
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Started by ManUtd67
Interested in opinion on whether to install a pre-leach thickener ahead of a gold leach circuit or operate cyclone at higher density. Option 1 - Cyclone O/F at 35% solids, P80 75um.  Thicken to 65% solids and dilute with tails thickener O/F (cyanid...
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Last replied to by rob riggir
Hi, It is better to go with the preleach thickener as long as you have the project life to get payback. You will then be able to operate your mills and cyclones at optimal densities and increase tan...
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978
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Started by Azadeh
I try to size and select two ball mills, which the first is in open circuit with feed rate of 125 t/h and its discharge goes to the sump of hydrocyclone and together with discharge of second ball mill, enters to the cyclone for classification. the se...
Last replied to by SmartDog
Simple answer:  yes 125 x 2.5 = 312.5.  In actual fact you need to to consider the size distribution of the new feed going to the mill, the grind characteristics of the new feed, the performance of ...
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Started by John Leumas
I am looking for information on methods to weigh or count grinding balls being added to a large SAG mill. We have rotary feeders and launders that allow balls to roll by gravity from the launder to the SAG mill belt conveyor about 50 ft upstream of t...
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Last replied to by superiorsam
I have seen a laser of sort that balls roll past to count but had problems. Also, load cells on hopper, magnet on load cell if using magnet to load balls. Some units are also more controlled and onl...
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Started by Jorge Quintanilla
Hello everyone. I am working on a new mining project in Bolivia. The listed mills are: METSO 9x13 Feet Ball Mill with 500 HP motor METSO10.5x14ft Rod Mill with 700 HP motorThe design of the foundation for dynamic equipment consists of two parts, t...
Last replied to by SmartDog
First off the static load is not just the weight of the equipment, it also includes the charge and the feed (ore + water).  The dynamic load is the static load + the impact load of the cascading medi...
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Started by mardin
Hi dears What is the effect of the size of the vortex finder at cyclone? the small size or tall size?
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Last replied to by Jorge
Follow the link below, https://www.911metallurgist.com/blog/hydrocyclone-workingprinciple    
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Started by adbcbd
Hello,  I have around 10 Kgs in total of different stone ores like sulfur and quartz and stibnite that I need to grind to 1.5mm.  However, I don't want to pay much and don't have so much free time to spend grinding. I tried to search for solution...
Last commented on by SmartDog
Time vs money
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Started by Partha@Mech
E= 10 Wi (1/√P80- 1/√F80) E= Specific Energy, Wi= Work Index,P80= Output,F80= Feed After this we need to multiply certain factors such wet/dry Factor, Separation Factor, Dia. factor,  Open/Closed Circuit Factor etc.. E= 10 Wi (1/√P80- 1/√...
Last replied to by David
"Awaiting for real answers based on research" Really? And you want this.... for free? You should contact info@bhagawati.com They are expert at this and certainly should be able to answer this very...
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1317
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Started by psvssharsha
How to control Ball mill grinding & classification circuit without DCS system for effective control on continuous operation
Last replied to by David
Hello C yes, Saeed is correct. Power-draw is your main driving factor. % Solids out of the mill is next. You will play around and identify what the optimum % Solids is for your situation. Personally,...
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Started by Ilkaar
Dear all,  What can be the causes of coarse balls ejection from a ball mill? this happened after liners replacement.  
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Last replied to by htnenado
Any increases to density within the mill when the ball loading is high can cause the balls to discharge. Keeping the BM % solids low will allow you to operate with higher loading but the mill becomes ...
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Started by Millza79
For an existing concentrator (with existing installed crushers and mills) where a new deposit is being locked at. What comminution tests should you do? I would have thought SMC and BBMWI are a must, with maybe UCS and crushing impact tests also impo...
Last commented on by Alex Doll
hmm, the parser screwed up the maths. It was supposed to say "current ore RWi much less than BWi, but new ore RWi much greater than BWi", then...
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Started by weethengtan
Hi, there. Currently our open-circuit, wet overflow rod mill 6ft x 12ft, feed size
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Last replied to by weethengtan
Hi Alex, Thank you for your guidance. I came across a relationship in an article stating Q = k*L*D^2.5 where Q is capacity and k is a constant. It's great to find similarity with your relationship in ...
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Started by banyechan
Our customers in CaCo3 grinding fileds,just sent us operating conditions in grinding.What types of balls are better for drying grinding?  
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Last replied to by weiliu2002
Cast balls are better for drying grinding and forged balls are not. In a drying grinding circumstance, working temperature of balls can reach to 300 above which will temp the forged balls and therefor...
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1083
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Started by Brendan158
Hello Mets, I'm looking for information around rod mill media size selection to prevent rod tangling. There is the rule that the length of the mill/rod should be 1.4 to 1.6 times the diameter but there is very little information on if there is a min...
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Last replied to by Brendan158
How does make-up rod diameter affect the risk of tangling?
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Started by akfury
Running flat gold & Garnet through impact mill / grinder. Will the gold roll up into a ball somewhat? I'm talking 20- concentrates.
Last commented on by SmartDog
Other than by hand, no
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Started by Jorge Quintanilla
Tin Ore Classification  One of the most recent tin projects in Bolivia involves the classification into four ranges:1. -1,800 micron +850 micron2. - 850 micron +212 micron3. -212 micron +45 micron4. -45 micron +30 micronTo obtain this classificatio...
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Last commented on by Jorge Quintanilla
Excellent observation. I appreciate the comment that helps us in making decisions
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1128
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Started by Namo2014
I need help on calculating (formula) SAG Mill volume solids and what a power load curve means? I have attached a sample of bearing press vs power draw for one of our SAG mills. Could someone help me with what my load curve means?  
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Last replied to by Jorge
Follow the link below, https://www.911metallurgist.com/ag-sag-grinding-circuit-automatic-control/
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Started by Saghar
Hello, I am working on air classification operations in a cement plant. The final air classifiers (High efficiency type, manufactured by polysius) have high values of bypass, let's say around 40%. I wanted to know what are common practices to reduce ...
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Last commented on by Saghar
That was very useful. Thanks I will declare the results if I can change the feed rate of the classifier
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Started by Saghar
Can anyone kindly help me determine selection function and breakage function in a laboratory rod mill? I need a reference that completely describes the process of determining grinding kinetics in rod mills
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Last replied to by Saghar
Thanks for answering. I have determined the selection and breakage function in case of ball mills previously, using modified H&F method. Now I need to know that how different is the procedure for a r...
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Started by Dachmann
Hello, I was told in this forum that economic efficiency is one of the major reasons for the ongoing popularity of Tumbling Mills in mineral processing. Concerning my questions I need some insight of experts with practical experience. Looking at SA...
Last replied to by David
A case by case trade off is to be done. Farnell Thomson Montreal based could do this. Here is a paper you will find useful.

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