a new approach to evaluating the performance of regrinding mills

a new approach for evaluating the performance of industrial regrinding tumbling ball mills based on grindability and floatability - sciencedirect

a new approach for evaluating the performance of industrial regrinding tumbling ball mills based on grindability and floatability - sciencedirect

The study develops a new approach for determining the performance of regrinding tumbling mills.The approach combines the grindability and floatability characters through regrinding systems.The final index defined as mean of the grindability and floatability indices.The applicability of this approach was validated using several industrial surveys.The performance ratio of 58% was calculated for the Sungun regrinding mill.

This paper aims to develop a new approach for determining the performance of regrinding tumbling mills, which is based on the grindability and floatability of locked particles through regrinding systems. The approach combines the grindability factor, in which the grinding of coarse particles is only considered, with the floatability of the regrind mill feed and product using the corresponding graderecovery curves. The approach was examined in the Sungun industrial regrinding tumbling ball mill using various feed rates. The results showed that the efficiency of the regrinding mill is extremely low and some practical approaches and means are proposed to enhance its efficiency.

selecting a regrind mill - grinding & classification circuits - metallurgist & mineral processing engineer

selecting a regrind mill - grinding & classification circuits - metallurgist & mineral processing engineer

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.

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?

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.

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.

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.

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:

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.

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.

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.

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 manufacturers 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 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.

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.

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.

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.

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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