Pore Connectivity and Dewatering Mechanism of Tailings Bed in Raking Deep-Cone Thickener Process
Farzad Daliri
Round 1
Reviewer 1 Report
I'm satisfied with the revisions made by the author based on the questions I asked.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
General comments:
The authors describe the use of X-ray computed tomography (CT) to study the connectivity and structure of pores at different heights in a flocculated settled bed produced in a laboratory column system. Although important experimental details on the acquisition of CT images are missing, as noted below, the paper’s conclusions are consistent with findings from other published studies using different techniques (some pertinent literature is not cited, however, as highlighted in the comments below).
It’s unclear why the authors mention “mature fine particles” in the Introduction and “mature fine tailings” in the Discussion. This terminology is used to describe the tailings produced in the oil sands industry and contained or “matured” in ponds for 3–5 years. This mature fine tailings (MFT), contains 30–40 % solids by weight, mostly as clays < 2 µm, and residual bitumen. It’s distinctly different from the vanadium-based flotation tailings used in the current study. References to mature particles or tailings are confusing and should be removed.
The level of English should be improved in any revision, and while this may not be the authors’ first language, there’s really no excuse for the many incorrect references to figure numbers throughout the text, which suggests that the paper was not carefully proof-read before submission. Similarly, the authors incorrectly refer to results for “maximum” pore volumes in the Discussion when in fact they mean “average” pore volumes – again, this is something that would have been easily picked up had more attention been given by the authors.
Specific comments are given below:
Line 19: Abstract – the abbreviation CT should be spelt out
Line 25: Abstract – in bed = in the bed
Line 27: Abstract – “the pores quantity decreased from 201 to 158”. The absolute number here are not important, but the decrease could be shown as a percentage.
Line 28: Abstract – “12.42%, 9.26%, and 2.97%, respectively”. The word “respectively” doesn’t fit here as the sentence starts with just two heights – the bottom and top positions.
Line 36: Introduction – “environmental maintain” is not clear and should be rewritten.
Line 39: Introduction – “environmental friendship art” is an ambiguous term and needs rewriting.
Line 42: Introduction – “improve” = improves
Line 43: Introduction – “pump” should be “pumping”
Line 44: Introduction – “backfill(CPB)” missing space
Line 46: Introduction – “wastewater . The mature fine particles”. Punctuation and spacing errors.
Line 55: Introduction – Liu et al [16] studied “special additives” – this term is vague and a better description should be used.
Line 53, 56, 78, and many more: Introduction - citations in the text should not include first names and initials (e.g. RK Dwari et al., Sharna MGlover et al., Philip Ofori et al.)
Line 56: Introduction – “Yang.” No full stop required here.
Line 63: Introduction – The authors state “Melbourne University and CSIRO center in Australia have published outstanding results on the theoretical model of thickener in continuous state”. This is a strong statement that should be supported by relevant literature. Some examples, among others, are:
- Farrow et al. 2000. Consolidation and aggregate densification during gravity thickening
- Zhang et al. 2015. Designing thickeners by matching hindered settling and gelled suspension zones in the presence of aggregate densification
- Benn et al. 2018 Sedimentation and consolidation of different density aggregates formed by polymer-bridging flocculation
Line 67: Introduction – “double polymer flocculation”. It’s not clear what the authors mean by this term. Does it refer to split dosing of polymers or use of polymer blends?
Line 73: Introduction – “The dewatering from flocculated aggregates network has received great attention to improve the underflow density”. This is correct, though equally important is the ability to produce pumpable slurries that often have to be transported considerable distances to tailings storage facilities.
Line 75: Introduction – “Computed” = computed and “was widely used” = has been widely used.
Line 82: Introduction – The sentence “So far, the CT approach has been the optimal method to deep in the micro scale dewatering mechanism reveal” does not read well and should be completely re-written.
Line 96: Materials and method – “a iron mine” = an iron mine. “The tailings are neutral to alkaline” = The tailings pH is neutral to alkaline. “The specific gravity of tailings” = The specific gravity of the tailings...
Line 112: CT scan test – the results refer to four different heights from which samples were taken in the settled bed. It should be made clear from which position is the height measured from, e.g. is it the height from the bottom of the cone section or the bottom of the cylindrical section of the column? Also, there is very little detail on how the CT images were captured. Were the images taken “in-situ” whilst the settled bed was still in the “settlement column” or was it necessary to collect samples from different heights in the bed? If the latter, how was this done to minimise changes in the material during sampling and how was material presented to the CT instrument to prevent sample movement over the duration of the test?
Line 117: “Three demission reconstruction” – any level of proof-reading should have picked up the spelling error – dimension.
Line 139: “flocculent particle” – Ignoring the misspelling of flocculant, the use of the word “particle” seems inappropriate. Flocculant chain?
Line 147: Results – what is “resistance time”? Residence time? What is the definition of “the top layer” on line 148 and how is the solids concentration determined?
Line 155: Results – “…without, with shear is 49.90 wt%, 44.18 wt%” = without and with shear is 49.90 wt% and 44.18 wt%.
Line 161: “as shown in Fig. 4”, Line 177: “column of Fig. 4”, Line 210: “as shown in Fig. 5”, and Line 233: “shown in Fig. 8” are all referring to the wrong figures !!!
Line 163: Results – “location in tailings bed” = location in the tailings bed. “Four tailings aggregates” = four.
Line 172: “the flocs start to sedimentation” should be re-written.
Line 192: Discussion – is equation 4 missing a “B” in DimB(down)? Also, the following sentence on line 193 “If the value of a formula is equal to the value of a formula” makes absolutely no sense!
Line 210: “The quantity of pores decreases with the bed height” should be rewritten to make clear that the number of pores decrease with increasing height in the bed. The final sentence in this section does not read well - “There are large size but less quantity pores at the top of the bed, formed long length and large diameter flow channel for sealed water drainage. I’d suggest rewriting to “There are larger but fewer pores at the top of the bed, forming longer and large-diameter flow channels for sealed water drainage”.
Line 217: Pore volume change – It seems the authors have made an error here when referring to the maximum and average pore volume results. It doesn’t make sense that the maximum pore volumes would be less than the average pore volumes at corresponding heights in the bed. From reading the abstract, it appears the authors have almost certainly mixed up the two data sets here. I also question the need for two and three sets of significant figures given the resolution of the CT instrument.
Line 225: Figure 8 – the Y-axis title is “voxel” but is it better represented by “Pore size” in units of voxel?
Line 339: Re-write to “changes from a dense to a loose state”
Line 243: “When the shearing effect adopted,…” would suggest changing this to “With shearing,…”
Line 248: Change sentence to “The water within the pores seeps upward through the bed under the shearing”.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The paper presents micro pores structure of flocculated paste tailings using experimental and analytical approaches. Even though the topic is interesting and could be very useful for dewatered tailings technologies, I would rank the overall quality of the paper in low level. the authors need to extensively work on the following issues to be able for the manuscript to be published as a journal paper:
1) The methodology and experimental approaches have not defined and explained properly. The authors are requested to modify these sections.
2) English language of the paper needs to be extensively improved.
3) Discussion and conclusion sections of the papers have focused more on quantitative results rather than scientifically explain the results. The authors have not specified how these results can facilitate dewatering techniques.
In addition to these major issues, I have the followings minor comments:
Line 36: “tailings surface disposal” and “underground CPB”
Line 37: “Low solids content?”
Line 40: Grammatical error
Line 43: PPT is not slurry tailings and might be confusing for readers. Remove “slurry”
Line 96: an “iron” mine
Line 98: Does the level of accuracy of SG, Density, etc require 3 digits decimal?
Line 98: What does “tailings porosity” mean? Is it a constant soil property or can be varied with solids content? Since void ratio is attributed to solids content, I do not think you need to specify this value in this paragraph.
Line 108: “g/t” means gram per tonnes of solids? Please specify?
In overall, I do not see a potential for this manuscript to be published in the journal until major revisions are addressed by the authors.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The authors have addressed all the comments/suggestions raised during review and have made significant improvements to the writing and style.
As a minor point, it is difficult to distinguish the four data series in Figure 8. A "zoomed" inset Figure could help in this regard, but this is more a suggestion than a requirement.
Reviewer 3 Report
The authors have improved the previous version and most of my comments are addressed. The English language has improved extensively; however, the authors are recommended to address all grammatical issues and proofread the text to avoid grammatical errors.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
- The paper has several grammatical and punctuational mistakes. Please make sure that all these mistakes are corrected before the final publication.
- The test platform in figure 1 is a vague picture. It would be better if a schematic is provided or a labeled photograph indicating different components of the test platform is provided.
- Figure 2 is unnecessary.
- The numbering in the material and methods section is incorrect.
- Discussions about separation and connected pore modeling in the material and methods section are inadequate. Please give more discussions on how the three-dimensional reconstruction process was conducted.
- The results of pore volume change (figure 7) can be combined in one graph for easy comparison with bed height.
- The conclusion should try to connect between the different results of porosity, pore numbers, pore volume change and distribution, fractal distribution etc and discuss the implication of this in the dewatering effect with bed height.
Reviewer 2 Report
The topic and originality of the manuscript are very good, but most concern I have is the English language. It needs a significant improvement on the manuscript prior to considering the publication. I also have several comments on the manuscript as listed below:
- Need a standard system to calibrate the CT results - the authors provided a sound correlation on the porosity, pore volume, number, and distributions with solids contents of tailings at different depth, but without a validated system to check, I am not comfortable to accept any claims that the authors has made.
- Need to describe the flotation tailings in terms of the particle size distribution, as the data is important for the correlation with the discussion of porosity.
- Need to pay attention to the units of the terminologies used in the manuscript, such as the slurry concentration at line 143, 146-147 and average porority in line 149.
- Line 203. Need to define the true size distribution vs color. Without it, any discussion related to the size and color is invalid.
