Grinding & Classification Circuits

Grinding & Classification Circuits 2017-03-23T09:46:37+00:00
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Selecting a Regrind Mill (13 replies)

Jean Rasczak
1 year ago
Jean Rasczak 1 year ago

Does the choice of regrind mill and mill media affect downstream flotation performance? As it relates to http://www.sciencedirect.com/science/article/pii/S089268751400140X

Until recently little attention has been paid to the effect of size on flotation. This has been especially true of material finer than 200 mesh.' Particles of different sizes must behave differently in a flotation circuit; increased information along this line would be of practical use as well as of theoretical interest.

Zander Barcalow
1 year ago
Zander Barcalow 1 year ago

One should note that there are several breakage mechanisms in any tumbling mills. The predominant mechanisms range from impact to attrition. One is dominant in SAG other one is more dominant in ball milling. As all we know SAG uses mostly impacts, however ball uses both impact and good amount of abrasion that is supposedly take all the added collector from the surface. Single categorization for tumbling mills as impact is quite insufficient. In addition, from this article it is understood that ball milling is quite inefficient due to high abrasion. Any other choice?

Ace Levy
1 year ago
Ace Levy 1 year ago

Please see our research about regrinding mill in Sungun copper concentration plant. Its topic is “A new approach for evaluating the performance of industrial regrinding mills based on grindability and floatability” and published in minerals engineering journal.

Bill Rico
1 year ago
Bill Rico 1 year ago

I think that it is better that we consider pulp chemistry changing in feed and product.

Volume 49, August 2013, Pages 116–120

Sugar Watkins
1 year ago
Sugar Watkins 1 year ago

I would like to split you question into two parts: first let us answer whether the choice of regrind mill and mill media affect the characteristics of the product from the total comminution circuit; depending on the answer to this , we should proceed to answer you full question.

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

This is a very appropriate discussion, we were only discussing today how we can combine our fine grinding expertise with our flotation expertise, and ways in which we can optimise both processes as a package.

Dizzy Flores
1 year ago
Dizzy Flores 1 year ago

These days, regrinding is becoming increasingly common due to the need to process more and more low grade and complicated ores. Regrinding not only further reduces particle size and increases the liberation but also produces new surfaces and changes the pulp chemistry, both of which are critical for subsequent flotation. Therefore, we believe it is important to study the influence of various regrinding conditions (e.g. grinding media, pulp chemistry, particle breakage) on subsequent flotation through the modification of particle surfaces.

Apart from the effect of particle breakage mechanisms on subsequent cleaner flotation, we have also conducted some studies focusing on regrinding chemistry, some results have also been published on Minerals Engineering:

1. The separation of chalcopyrite and chalcocite from pyrite in cleaner flotation after regrinding, Volume 58, April 2014, Pages 64–72

http://www.sciencedirect.com/science/article/pii/S0892687514000119

1. Importance of oxidation during regrinding of rougher flotation concentrates with a high content of sulphides Volumes 66–68, November 2014, Pages 165–172

http://www.sciencedirect.com/science/article/pii/S0892687514001241

I believe there are still a lot of research work we need to do since regrinding is becoming more common and we will identify more problems. I hope we can get more interesting comments and discussions here, which will be highly valuable for our future research.

Marshal Dienes
1 year ago
Marshal Dienes 1 year ago

Were able to accept the fact that regrinding mill and mill or grinding Media affect downstream performance or not. The system will contain a lot of circulation loads, and as you know if you have more circulation loads, your impact and abrasion performance in SAG and BALL MILL will not be effective, and your pulp too will be affected.

Marshal Meru
1 year ago
Marshal Meru 1 year ago

As a grinding media designer we have had customers specify media chemistries as they have less consumption of their flotation agents in the downstream process. We did look at this closely and have found that some floatation agents do indeed have higher consumption with higher fe ball content. In checking this we have found that other floatation agent makers do not have that problem. In conclusion the higher Cr balls were not needed, just changing the chemical supplier allowed the use of more economic media.

Just one piece of your puzzle.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

I can say that my experience from conducting flotation testwork programmes over the years has been that at least in some ores the type of regrind media used can have an effect on subsequent flotation. For example, gains in recovery and/or grade are seen when using a high-Cr or an inert ceramic-type media over that seen with mild steel.

However, as Mark has mentioned above it would also be necessary to trial alternative reagents to determine whether the effect is consistently seen or an artifact of using a particular manufacturer’s product / type of reagent.

Obviously any decision on the type of media to use in the plant will need to weigh up the additional costs of specialist media against any additional revenues from extra recovery or savings in reagent costs.

The part above dealt purely with the chemistry of the media.

The second issue is that of breakage mechanism. Alumina and other ceramic-type media are significantly less dense than steel. My experience is that using a similar charge size distribution in a similar tumbling mill will typically require a longer grind time to achieve the same target p80. The breakage mechanisms and characteristics must therefore be different and this in turn will have an effect on surface chemistry and reagent adsorption.

So it appears that we are seeing both a physical effect in breakage characteristics and an effect from the chemistry of the media.

My experience of media effects comes from conducting regrind tests during project testwork where we were only looking at results to determine whether grade and/or recovery could be improved in subsequent cleaner stages. Further investigative work would be required to fully understand the mechanisms involved and their relative contributions to downstream performance.

Carl Jenkins
1 year ago
Carl Jenkins 1 year ago

The efficiency of the classifiers is also important when we look at the regrind circuit and not just the mills. Creating slimes is not going to help flotation. The achieved classification efficiency at full scale can be quite poor (in my limited experience). Simple preventative maintenance practices can make dramatic differences.

Marshal Dienes
1 year ago
Marshal Dienes 1 year ago

For simulation of regrind mills I developed a model many years ago.

http://www.sciencedirect.com/science/article/pii/S0892687503004308

this model was particularly advanced as it considered multi-mineral particles.

It is one of the reasons I developed an independent simulator (MMVisioSim) as there was no opportunity to integrate such an advanced model in other simulators.

So if anyone is specifically interested in simulating regrind and linking to flotation, please connect and we can discuss further.

Sugar Watkins
1 year ago
Sugar Watkins 1 year ago

Recently, we examined the floatability of regrind feed and discharge in the various size fractions in Sarcheshmeh Copper Complex (Cu mineral was Chalcopyrite).

We observed that, particle size decreased significantly due to regrinding while floatability of the feed was more than discharge. Moreover, floatability of each fraction (e.g. -400, +400-325) in mill feed and discharge was studied. Results indicated that, the floatability of all fractions in the mill feed was more than the mill discharge. It means that electrochemical interactions between the grinding media and Chalcopyrite let to decrease in floatability of material.

Carmen Ibanz
1 year ago
Carmen Ibanz 1 year ago

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 chalcocite surface is oxidized by oxygen. On the chalcocite surface is xanthate are oxides and hydroxides of iron and copper. Therefore, chalcolite is not floated.

2. to floating chalcocite from the tails need dissolved the iron and copper oxides by sulfuric or chloric acid at pH 1.4. Xanthate is decomposed to free sulfur, oxides and hydroxides until sulphates. Then the chalcocite surface will be very hydrophobic.

3. For such flotation may be used the pachucs if the particle size is less than 74 microns. If more then, pachucs flotation will not be due to the high pressure of the pulp. This flotation should be performed in shallow machines.

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