Optimization of Microwave Reductive Roasting Process of Bauxite Residue
Round 1
Reviewer 1 Report
The results obtained in the study are relevat from the point of view of metallurgical waste treatment. The article may be accepted but minor revisions are required. Please, find the reviewer's reccomendations in the file attched.
Comments for author File: 
Comments.pdf
Author Response
We wish to thank the reviewers for their interest in our work and for helpful remarks that will improve the manuscript. We believe we have addressed all of the major comments and we appreciate the opportunity to clarify our research objectives and results.
As indicated below, we have checked all the comments provided by the reviewers and made necessary changes accordingly to their indications.
Please see the attachment
Author Response File: 
Author Response.docx
Reviewer 2 Report
Comments to the Authors.
The paper describes the influence of the operation conditions for the microwave assisted reductive roasting of red mud with the aim of valorising this waste from the alumina industry. The reviewer thinks that this is an important topic and will be of high interest for the readers of the journal Metals.
- Manuscript comments:
Taking into account, the low penetration depth of microwave irradiation. Can the authors justify why the use pellets rather than a powder mixture to carry out the experiments?
On page 5 Line 148 the sentence “The chemical analysis results of metallurgical coke presented in.%.” seems to be incompleted
Can the authors say what was the irradiation time for the experiments shown in Figure 4?
On the results section, it can be observed a decrease of the absorbed microwave energy at different power capacities. The explanation to this observation must be related with the different mineral phases formed after the sample treatment. I recommend the authors to read the reference Sanchez-Segado, S., Monti, T., Katrib, J. et al. Towards sustainable processing of columbite group minerals: elucidating the relation between dielectric properties and physico-chemical transformations in the mineral phase. Sci Rep 7, 18016 (2017) as a guidance.
On the conclusions section, page 15 line 360, the authors claim that the temperature reached in the experiments was 1100ºC. However, Figure 5 shows that the maximum temperature reached was below 1050ºC and it was decreasing with time. Can the authors clarify this issue?
Author Response
We wish to thank the reviewers for their interest in our work and for helpful remarks that will improve the manuscript. We believe we have addressed all of the major comments and we appreciate the opportunity to clarify our research objectives and results.
As indicated below, we have checked all the comments provided by the reviewers and made necessary changes accordingly to their indications.
Please see the attachment
Author Response File: Author Response.docx
Reviewer 3 Report
Dear authors,
the paper describes roasting of bauxite residues by microwave heating. It represents an interesting and important contribution to modern handling of industrial by-products, to zero-waste-managmenet strategies, and to transform an industrial process to lower carbon intensity.
The procedures are clearly discribed and the paper is well written.
In have only few suggestions for text improvements and few remarks on typographcal errors below.
And one remark:
Could you please roughly estimate the energy requirement for the investigated microwave roating process, e.g. in kWh/kg product, from your optimized experiments. This would be interesting to compare with alternative process options, and to provide some preliminary data for a possible industrial pilot project. (Of course, there are some restictions to scale from laboratory to pilot plant.)
suggestions for the manuscript:
line 171: ... of BR by changing the amount of MW energy ... -> ... of BR on power conversion during the roasting process. ...
Merge Fig. 9 into Fig. 10. Interpretations and conclusions in the the text remain the same.
suggestion for line 341: ... optimized sinter can be considered a drawback ... -> ... optimzed sinter represents a drawback ...
and few typos:
- line 42: In the las -> In the last
- line 79/80: reference missing.
- line 148: in wt.%
- line 332: reference missing.
- line 340: can be considered
Best regards.
Author Response
We wish to thank the reviewers for their interest in our work and for helpful remarks that will improve the manuscript. We believe we have addressed all of the major comments and we appreciate the opportunity to clarify our research objectives and results.
As indicated below, we have checked all the comments provided by the reviewers and made necessary changes accordingly to their indications.
Please see the attachment
Author Response File: Author Response.docx
