Exploring the End-Liner Forces Using DEM Software

Round 1

Reviewer 1 Report

The idea of the work is interesting and the presented DEM solutions are needed for areas using SAG mills. However, I miss the mention of calibration, validation and other parameters that would increase the credibility of this work.

Some mistakes that should certainly be removed if the authors decide to republish:

• Name of software Itsaca VS. Itasca - chap. 2.1
• Table 1: both values and units of Shear stiffness 3 x 106 KN need to be corrected.
• Figure 2: it is not entirely distinguishable which curve is for radial and tangential forces
• Figure 3: the force units are in N and in the text in kN, the shift of the values of sectors 2 and 3 by 20 kN (N) can be confusing.
• There are discrepancies between Figure 3 and 5. Where is the 0 ° mark in Figure 5. The described peak at 70 ° in Section 1 is not apparent.
• It is not entirely clear what is meant by Mill end 1 and 2
• Densities and weights of spheres in DEM are not given

Author Response

Minerals

Exploring the End-Liner Forces Using DEM Software

 

Dear Reviewer

 

RE: LIST OF CHANGES ON THE POINTS RAISED

Thank you for your useful technical comments and suggestions on our manuscript. We have modified the manuscript accordingly.

 

Detailed corrections are listed below point by point. Points raised are in italics and changes made or our response to those points in normal text.

 

Reviewer #1

The idea of the work is interesting and the presented DEM solutions are needed for areas using SAG mills. However, I miss the mention of calibration, validation and other parameters that would increase the credibility of this work

• Thank you

 

Some mistakes that should certainly be removed if the authors decide to republish:

Name of software Itsaca VS. Itasca - chap. 2.1

• The name was corrected.

Table 1: both values and units of Shear stiffness 3 x 106 KN need to be corrected

• The 6 is superscripted to show that it is exponential.

 Figure 2: it is not entirely distinguishable which curve is for radial and tangential forces

• The figures were redrawn in colour to distinguish the curves.

Figure 3: the force units are in N and in the text in kN, the shift of the values of sectors 2 and 3 by 20 kN (N) can be confusing.

• Values were changed to N in the main text.

There are discrepancies between Figure 3 and 5. Where is the 0° mark in Figure 5. The described peak at 70 ° in Section 1 is not apparent

• The discrepancies were addressed when the figures were redrawn.

It is not entirely clear what is meant by Mill end 1 and 2

• Comparison changed to Long end-lifters and short end-lifters

Densities and weights of spheres in DEM are not given

• Density and ball mass are given in Table 1

 

The authors would like to thank the reviewer once more for the constructive comments that help to improve the quality of our work.

 

Kind regards,

Reviewer 2 Report

The article is well-written and presents a fundamental DEM analysis of the radial and tangential forces acting on grinding mill end-liners. The purpose of the study is to "understand end-liner wear and damage".

While the article provides details of the forces acting it is recommended that the impact and shear intensity (i.e. W/m^2) also be evaluated and discussed to add to the scientific contribution of the research. Without this analysis, or similar, little can be concluded in relation to wear.

The 20 and 40N offsets of the data in Figures 3, 5, 7,9 and 10 is confusing. It would be best to use three individual plots positioned vertically. This will still allow for adequate comparison.

References to the work of Cleary are incorrect i.e. "Clearly" on page 2.

 

Author Response

Minerals

Exploring the End-Liner Forces Using DEM Software

 

Dear Reviewer

 

RE: LIST OF CHANGES ON THE POINTS RAISED

Thank you for your useful technical comments and suggestions on our manuscript. We have modified the manuscript accordingly.

 

Detailed corrections are listed below point by point. Points raised are in italics and changes made or our response to those points in normal text.

 

Reviewer #2

The article is well-written and presents a fundamental DEM analysis of the radial and tangential forces acting on grinding mill end-liners. The purpose of the study is to "understand end-liner wear and damage".

• Thank you

While the article provides details of the forces acting it is recommended that the impact and shear intensity (i.e. W/m^2) also be evaluated and discussed to add to the scientific contribution of the research. Without this analysis, or similar, little can be concluded in relation to wear.

• Table 2 showing peak forces and average forces for each of the sections and discussion have been included in Section 3.1.4

The 20 and 40N offsets of the data in Figures 3, 5, 7, 9 and 10 is confusing. It would be best to use three individual plots positioned vertically. This will still allow for adequate comparison

• The three individual plots were positioned vertically as suggested by the reviewer in all the figures.

References to the work of Cleary are incorrect i.e. "Clearly" on page 2.

• The spelling of the reference was corrected

The authors would like to thank the reviewer once more for the constructive comments that help to improve the quality of our work.

 

Kind regards,

 

Reviewer 3 Report

See the attached document.

Comments for author File: Comments.pdf

Author Response

Minerals

Exploring the End-Liner Forces Using DEM Software

 

Dear Reviewer

 

RE: LIST OF CHANGES ON THE POINTS RAISED

Thank you for your useful technical comments and suggestions on our manuscript. We have modified the manuscript accordingly.

 

Detailed corrections are listed below point by point. Points raised are in italics and changes made or our response to those points in normal text.

 

Reviewer #3

This paper deals with the modelling on a lab scale horizontal ball mill by means of DEM. The authors present a comprehensive numerical study on how the end liner design, ball-size distribution and mill filling influence the end-liner forces. The manuscript provides further insights into the force environment of ball mills and the reviewer considers it to be an adequate contribution that aligns well with the scope of the journal. The outcomes are beneficial for the wider industrial use of ball mills and further the knowledge on the effect of the end-liner design on the mill performance. Thus, the proposed modelling strategy and investigations could potentially serve to improve the mill design and operational conditions. The manuscript is well-structured with a clear methodology and an appropriate interpretation of results.

• Thank you

Prior to publication, the reviewer suggests a revision of the manuscript by addressing the comments below.

 

In the materials and methods section the authors briefly presents their DEM implementation. However, this section is very brief. The reviewer suggests that it is extended to include a description of the contact law used for the present DEM implementation, both for DE-DE and DE-mill contacts. The DEM parameters are of fundamental importance and how the authors selected the parameters used in the present study should be addressed. Furthermore, the number of DE elements used in the simulations and the material of the balls should be given. Also, it would be interesting to know the time required to run the simulations.

• The contact model is mentioned and an additional reference that explores this further is included. The collection of forces acting on the end-lifter sections is also briefly discussed.

The presentation of forces acting on the different section of the end-liners is somewhat confusing, e.g. in Figure 3. The reviewer suggests that the presentation of forces is not made by incrementing the different section forces, but instead separate y-axes could be used. The reader of the paper should be able to understand the figures without referring to the text. In the present form, this is difficult.

• The figures were redrawn and presented as per the reviewer’s suggestions.

In Figure 4, the authors present a comparison between their simulated ball movements with experiments. The mill used for the experiment seems to be of a different design though, e.g. the number of shell liners is different. The reviewer is of the opinion that this comparison is superfluous and could be addressed in text only.

• Fig 4a is not a simulated mill presented in Fig. 4b. The authors provided Fig 4b as a reference to consolidate their analysis about the pattern of charge motion in the mill.

On line 207, the authors state that there is a clear indication that larger balls can cause more damage on the end-liners. At the same time, the power draw increases for the smaller balls which might be an indication of increased energy dissipation due to friction between balls and mill structure. Wear should not only be understood as an effect of impacts but also on sliding distance and pressure. The average shell liner force profiles are very similar for the different ball sizes but due to increased friction the wear can be substantially different between two. This should be addressed in the manuscript.

• The authors have added a statement suggested by the reviewer explaining the possible cause of the increase in power draw for small balls. As for wear; while the authors agree with the reviewer that wear should be understood in terms of impacts, sliding distance and pressure, they regard it as a subject worth of its own dedicated study, which they plan to do on end-liners in future, as published by Y.-x. Peng et al. (2017); Mahmud et al. 2018, among other researches. Nonetheless, the authors had already mentioned at the end of Section 3.2 that the study of wear is beyond the scope of this investigation.

Some minor comments.

The keyword wear studies should be removed since the paper is not addressing wear directly.

• The keyword wear studies was removed.

On line 125-126, it should say Section 3.

• It was corrected.

In Figure 7, the scale of the x-axis is different in (a) and (b), please use the same scale for easier comparison.

• The figures were redrawn and the problem was corrected.

 

The authors would like to thank the reviewer once more for the constructive comments that help to improve the quality of our work.

 

Kind regards,

 

Round 2

Reviewer 1 Report

Most deficiencies were corrected.

Reviewer 3 Report

The authors have provided answers to most of my queries and edited the manuscript accordingly.