Effective Desulfurization and Alumina Digestion of High-Sulfur Bauxite by New Roasting Process with Conveying Bed
Round 1
Reviewer 1 Report
Manuscript ID: processes-1122909
Title: Effective Desulfurization and Aluminum Digestion of High-Sulfur Bauxite by New Roasting Process with Conveying Bed
Authors: Bo Zhao et al.
The article presents studies on the removal of sulfur from bauxite, as well as leaching of roasted bauxite by alkali. A large number of experiments have been carried out; the results look reliable. The article will be of interest to a wide range of scientists studying the Bayer alkaline method and phase transformations in clay minerals.
There are several questions: it is necessary to significantly improve the introduction and the section devoted to phase transformations in the roasting process.
The article corresponds to the Processes and can be published after correcting errors.
Page 1:
For example, it caused corrosion of steel equipment. Add reference for this information (Initial corrosion behavior of 12Cr1MoV steel in thiosulfate-containing sodium aluminate solution, DOI: 10.3390/met10101283).
S22- in high sulfur bauxite undergoes gradual transformation into S2O3 2−, SO3 2−, and SO4 2− during the Bayer process, which leaded to adverse effects in production (add references for Sulfur Removal of High-Sulfur Bauxite, DOI: 10.1007/s42461-020-00225-6)
Use more new sources for desulfurization methods:
Flotation (Effects of fine minerals on pulp rheology and the flotation of diaspore and pyrite mixed ores, DOI: 10.3390/min10010060 /Enhanced separation of pyrite from high-sulfur bauxite using 2-mercaptobenzimidazole as chelate collector: Flotation optimization and interaction mechanisms, DOI: 10.1016/j.mineng.2018.09.017);
Roasting desulfurization (Desulfurization of pyrite in high-sulfur bauxite with microwave roasting process, DOI: 10.11817/j.issn.1672-7207.2020.10.003 / Review on Desulfurization of High-sulfur Bauxite, DOI: 10.11896/j.issn.1005-023X.2017.05.014 / Roasting pretreatment-low temperature digestion method for comprehensive utilization of high-sulfur bauxite, DOI: 10.1007/978-3-319-72284-9_1).
Table 1. What is the LOI content (loss on ignition)?
Table 2. Add full chemical formulas of minerals.
Section 2.2 Why used 90% N2 + 10% O2 atmosphere? Bauxite roasting in the air atmosphere, it has another composition between N2 and O2.
Table 3. Why authors did not write enthalpy data for last 2 reaction?
Page 7. Thermoanalysis results within the heating rate range of 15–50 °C/min show… Where this TGA/DSC figures?
Page 9-10. Description of Figure 6. After dehydration, both minerals are transformed into α-Al2O3 and Al2O3·2SiO2. It is not true information. Diaspore and kaolinite must change phases to γ-Al2O3 and Al2O3·2SiO2 (metakaolinite) during roasting (add link DOI: doi:10.1088/1757-899X/110/1/012049).
α-Al2O3 can formed only at 1200 º. Authors must change text and XRD peaks. Please, sign peak for metakaolinite and γ-Al2O3. See more at article: Decomposition of boehmite-kaolin bauxites by hydrochloric acid using preliminary calcination.
Figure 6. Where Fe2(SO4)3 phase at XRD?
Figure 7-8. Add figures use only temperatures, like 520 ºC. Add more information about leaching parameters at figures titles. What are the chemical and mineral composition of bauxite after leaching at optimal parameters? What are the S content in liquor?
Section 3.3 Add chemical reaction between roasted bauxite and alkali during leaching process.
Section 3.4 Authors write about metakaolinite obtained through rapid roasting… Please, add this phase to section 3.2 and figure 6. α-Al2O3 can not be in this bauxite, change it to γ-Al2O3.
Conclusion. Chapter 3. Add information about optimum leaching parameters and Al extraction degree compare to raw bauxite.
References. Add more links from Metals, Minerals, etc. from 2019-2021.
Technical errors:
Page 1: FeS2 and S22- must be change to FeS2 and S22-. Major desulfurization mothods – methods
Title of Table 4. ignition loss must change to loss on ignition.
Page 12. …from 14 nm at 520 °C to 20 nm at 780 °C... I believe that 780 °C must be change to 720 °C
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
This manuscript reports on the treatment of some kind of bauxite. After the following points are revised, this manuscript can be accepted for publication.
- Title : It is better to change aluminum into alumina in the title.
- The wt% of S in the sample was 1.35%. In this case, the effect of particle size is very important. However, there are no comments on this effect. This should be revised.
- It is necessary to comment on the kinetic aspects of desulfurization.
- In Eqs. (2)-(4), the rate should be replaced by percentage. In obtaining these percenatges,it is necessary to comment the method to reduce the effect of temperaure during cooling.
- In experimental, there are no comments on the analysis method of digetion liquid and red mud.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
Effective Desulfurization and Aluminum Digestion of High-Sulfur Bauxite by New Roasting Process with Conveying Bed is very interesting paper. Some minor improvements are required.
Abstract:
What is a value of the sulfur in high-sulfur Bauxite?
What is the Efficiency of Sulfur removal at 520‒720 °C for 2 s.
Please to correct: FeS2 to FeS2
I am sure that S22- is not correct (Maybe S22-). Please to improve it.
Page 4: the apparent residence time of bauxite powders in the reactor was approx. 2 s. Is residence time of 2s calculated ore measured value?
Page 4: According to the procedure requirements, ore pulp, which consisted of mother solution with a specific ratio for digestion, bauxite, and lime, was loaded into a 100 mL steel bomb and sealed. What is a quantity of ore pulp?
Page 8: Table 4. Analysis results of ore roasted at various roasting temperatures (Please to add the reaction time in s). Are you shute that dehydration reaction can be finished in 2 s?
Page 11: At X-Axis: Please to write: Digestion Temperature/°C
PAge 8: the rapid desulfurization of high-sulfur bauxite can be achieved in the conveying bed after approx. 2 s. Can you confirm this time of 2 s with some meaurement? Why did you not analyze the kinetics of process using different reaction time (for example 1s, 10 s, 60 s)
Page 8: Figure 5. Trend of sulfur mass fraction and the desulfurization of roasted ore ay various temperatures. Please to correct "ay" ("at").
Author Response
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Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
The authors have made major corrections in the article.
There are a number of comments for authors answers:
1) When you first write the name of a mineral, its chemical formula should be in brackets. Not all scientists know the chemical formula of dolomite or siderite or boehmite, etc. Your article may be of interest not only to those involved in the alumina production. These are the usual rules for article writing.
2) The enthalpy data in Table 3 is very easy to obtain. These are well-known reactions. If these reactions are not needed, authors can remove them.
3) Figures 8-9 do not have signs of degrees Celsius (°C)
Author Response
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Author Response File: Author Response.docx
Reviewer 2 Report
The current version of this manuscript can be accepted for publication.
Author Response
Thank you very much for your review!
