Kinetics of Smelting Chromia–Bearing Vanadiferous Titanomagnetite Ore via High–Temperature CO₂–Containing Gas Injection

Round 1

Reviewer 1 Report

In the paper through thermodynamic smelting experiments, non-isothermal and isothermal kinetics experiments, the effects of CO2-containing gas injection on the smelting of chromium-bearing vana-dia-titania magnetite were investigated. The article a lot of experiments and conclusions  was included. The article good topic and very good information was characterized. For me the article  a lot of good and new literature’s positions was included. For me the Authors may be consider graphic improvement of the drawings, especially - figures 16,19,20 - the numbers are too small - in figure 19 in my opinion the  musical notes is not good idea in scientific publication.

Author Response

Dear reviewer,

Thank you very much for your valuable and helpful comments. We seriously redesigned and rewritten the paper (Manuscript ID: metals-1218816). And we deeply appreciate your reconsideration of our manuscript.

All the figures you mentioned (Figure 16.19.20) have been corrected totally.

And Thank you again for your constructive suggestions!

 

Reviewer 2 Report

The article addresses the issue kinetics of Smelting Chromium-bearing Vanadia-titania Mag-2 netite via High-temperature CO2-containing Gas Injection. 

It deals with thermodynamic quantities, mainly kinetics. The topic follows a similar issue, which has already been published in Journal of CO2 Utilization.

Therefore, this study aims to reveal the metallurgical re- action kinetics of CVTM smelting. The feasibility and qualification conditions of large  pellet ratio and CO2 injection were explored. 

The effect of the injected CO2 concentration on the softening-melting-dripping  characteristics of CVTM was explored.

The use of CO2, which is mostly a waste material as a partial reducing agent, is environmentally and economically favorable. 

The results of the experiments are encouraging and the authors should continue with this issue.  

Author Response

Dear reviewer,

Thank you very much for your valuable and helpful comments. We seriously corrected the paper (Manuscript ID: metals-1218816) with all the reviewer's opinions. And we deeply appreciate your consideration of our manuscript.

And Thank you again for your constructive comments! We will continue to investigate this issue.

Reviewer 3 Report

The manuscript  is clear and with good quality, at a high scientific level. There is some unclear points that need to be repaired and state more precisely. I am sending a few comments:

 

Line 66-74:

It would also be appropriate to insert the chemical composition of individual materials, as phase analysis may not show all compounds. For example, the original ore is based on the Fe-Cr-Ti-V oxides, but XRD analysis does not show it.

 

Line 69:

I think the international label of basicity is B (B2).

 

Line 76 (Figure 1)

Diffraction lines from XRD analysis at some compounds are not marked correctly, please check it.

 

Line 88-93:

I think, softening zone is bounded by two temperatures (for example from 1035^oC to 1144^oC). [T40-T4] is softening interval (for example 109^oC). Similarly melting-dripping zone is bounded by two temperatures (for example from 1218^oC to 1414^oC). [Td-Ts] is melting-dripping interval (for example 196^oC).

 

Line 102 (Table 2):

Heating rate: - 5^oC/min

Probably heating rate is 5^oC/min

 

Line 142 (Figure 5):

Please correct lower index:CO₂.

Line 152 (Figure 5):

The viscosity calculation is not correct throughout the temperature interval, the dynamic viscosity (Pa.s) cannot be negative. I do not know the apparent viscosity in Pa.s with negative values.

 

Line 166-167:

Please specify reactions.

 

Line 177-178:

Please specify reactions.

 

Line 185:

Due to the various composition of the reaction atmosphere (gas mixtures) and samples, it cannot be considered for all models when loss weight only with reduction. In lines 177-180 you have text: „Therefore, it can be considered that the weight loss of the charge is caused by complex multi-interface reactions, and the valuable metal oxides may also participate in the reoxidation reaction in the reduction process“. The text is contradictory consideration in the equation (3).

 

Line 249:

I don't think that the charge begins to soften in lump zone. See next comment.

 

Line 263 (Figure 14):

Unclear distribution of reaction zones in blast furnace in lump zone (above cohesive zone can not be temperature 1200^oC), molten slag and iron is not in the cohesive zone. In the lower part of the cohesive zone, FeO-Fe₃C and the primary slag are formed, but it is not yet completely melted. In this cohesive zone is a physical process that is a change in solid for liquid and this gradually through the plastic state of different viscosity. It is not possible to consider completely molten slags and completely reduced iron oxides to iron in cohesive zone.

 

Line 292 (Figure 15):

The progress of the reaction is not completely accurate - the beginnings of reactions, number of reactions, stoichiometry. For example the beginning of reactions: 3TiO₂+C=Ti₃O₅+CO is at 1120^oC, 2Ti₃O₅+C=3Ti₂O₃+CO is at 1380^oC. Please check it. Also I have a problem with distribution zones in Figure 15. The softening temperature is usually associated with the first drops of melt observed. If the sample reaches a hemispherical shape, we speak of the melting temperature. The melting interval can be determined from the beginning of the softening to reaching a hemispherical shape. The melting temperature is not usually indicated when the first drops of melt are observed. In the case of the sinters (or pellets), it is better to indicate the melting interval, as the sinter contains several mineralogical components which melt at different temperatures.

 

Line 294 (Figure 16):

Some compounds are not seen, maybe it would be preferable to mark through arrows.

 

Line 321 (Figure 17):

It would be more appropriate figure a-d identify in legend and label them in the text above the Figure 17.

 

Comments for author File: Comments.pdf

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

The topic considered in the article "Kinetics of Smelting Chromium-bearing Vanadia-titania Magnetite via High-temperature CO2-containing Gas Injection" is interested since consider the topic of different raw materials for the blast furnace as well as its behaviour in the furnace. Even when it is a good manuscript, some questions could be improved/clarified as:

• Line 45: What other phenomena?
• In general, to frame the topic: What is the objective of using this kind of raw materials? What influence has this raw materials in the produced pig iron? 
• Line 48, what other questions involve the production of titanium carbonitride apart from the coke consumption and CO2 production, particularly for the composition of the product?
• Line 68: Why this mass ratio was used?
• Line 123: some additional explanation should be given about the behavior presented in the figures (in general), and in this particular case how can you explain this rise and fall.
• Line 134: maybe you missed "l" in the word "benefitial". Additionally, how can you explain that using 20 vol% CO2 you have similar behavior than using 0%? This is important since environmental and energy points of view (as you mention).
• Line 142: CO2, number 2 should appear as subscript.
• Line 147: sulphur value is low if compared with the other cases of the article or in general? What do you consider a low sulphur value?
• Line 150: HCG, please include definitions for all the abbreviations the first time they appear in the text.
• Figure 16: Text in this figure is not visible (particularly subscripts), please increase the size of the font or the quality of the image. Similar comment is applicable to other figures where subscripts or superscripts are used.
• I miss a paragraph at the end of the dicussion section where you indicate the industrial/practical relevance of the consequences deduced from the model. 

Author Response

Dear reviewer#4,

Thank you very much for your valuable and helpful comments. We seriously redesigned and rewritten the paper (Manuscript ID: metals-1218816). And we deeply appreciate your reconsideration of our manuscript.

The significant revisions as required include:

1. Line 45: What other phenomena? In general, to frame the topic: What is the objective of using this kind of raw materials? What influence has these raw materials in the produced pig iron? 

Re: The furnace pressure is abnormal, the furnace temperature is overheated, and the charge collapses. The expression of this sentence has been corrected. In fact, this raw material is the main raw material for the production of vanadium-containing molten iron. In China, the use of blast furnace smelting method to smelt it is relatively more mature. But obviously, due to the excessively high content of titanium oxide, there are still some problems hindering productivity and anterograde.

2. Line 48, what other questions involve the production of titanium carbonitride apart from the coke consumption and CO₂ production, particularly for the composition of the product?

Re: Titanium carbonitride forms inclusions in the molten iron, which adversely affects the subsequent molten steel and continuous casting products.

3. Line 68: Why this mass ratio was used?

Re: To keep a slag basicity required from actual production. (CaO/SiO₂ is about 1.1)

4. Line 123: some additional explanation should be given about the behavior presented in the figures (in general), and in this particular case how can you explain this rise and fall.

Re: Thank you for your helpful suggestion. In fact, this is directly related to the degree of reduction of each oxide in the slag and the melting point, melting rate and viscosity of the complex oxide system formed. However, due to space limitations, this article only provides directly influential results, the purpose is to explore the dynamics of the process.

5. Line 134: maybe you missed "l" in the word "benefitial". Additionally, how can you explain that using 20 vol% CO2 you have similar behavior than using 0%? This is important since environmental and energy points of view (as you mention).

Re: Thank you very much for your careful correction. The word has been corrected. What you asked is a good question. In fact, 0% is the control test group. It represents the way of hot air injection. 30% of CO comes from the reaction of O2 in the air and coke. The CO in the following experimental conditions comes from HCG itself. Therefore, this result shows that even if the CO2 reaches 30%, the worst is the same as the initial injection of air. Therefore, CO2 brings in more C than O2, so theoretically, the coke consumed is half of O2. By the way, in order to compensate for the endothermic reaction of CO2 and C, it is necessary to inject high-temperature gas (physical heat), which is also a part of energy utilization.

6. Line 142: CO2, number 2 should appear as subscript.

Re: Thank you for your correction. The word you mentioned has been corrected.

7. Line 147: sulphur value is low if compared with the other cases of the article or in general? What do you consider a low sulphur value?

Re: This means that there is no obvious surge, and it is maintained at a stable value. The expression has been corrected.

8. Line 150: HCG, please include definitions for all the abbreviations the first time they appear in the text.

Re: HCG has been made a definition in Line 51. “Therefore, the re-use of high-temperature CO₂-containing gas (HCG) injection to replace part of the hot air injection was studied.”

9. Figure 16: Text in this figure is not visible (particularly subscripts), please increase the size of the font or the quality of the image. Similar comment is applicable to other figures where subscripts or superscripts are used. I miss a paragraph at the end of the discussion section where you indicate the industrial/practical relevance of the consequences deduced from the model. 

Re: Thank you for your helpful comments. The figure has been pulled larger. The practical relevance of the consequences have added in the conclusions.

Reviewer 5 Report

See attached comments.

Comments for author File: Comments.pdf

Author Response

Dear reviewer#5,

Thank you very much for your valuable and helpful comments. We seriously redesigned and rewritten the paper (Manuscript ID: metals-1218816). And we deeply appreciate your reconsideration of our manuscript.

The significant revisions as required include:

1. Line 46, Reference numbers jump from [1, 2] on Line 39 to [8-11] on Line 46, before mentioning [3-7] on line 51. References need to be listed in numerical sequence when first mentioned. This needs to be corrected and all subsequent statements pertaining to references 3-11 need to be checked for accuracy.

Re: Thank you for your correction. All the references have been updated by Endnotes and listed in numerical sequence.

2. Line 82, “Their reaction conditions are shown in Table 2.” Should be “Their reaction conditions are shown in Table 1.” All subsequent references to tables in the text need to be corrected. At the present time there is no mention of Table 1 in the Ms.

Re: Thank you for your correction. The sentence and table title have been corrected as your mentioned.

3. Line 102, “Table 2. Reaction conditions.” Should be “Table 1. Reactions.” All tables need to be renumbered.

Re: Thank you for your correction. The sentence and table title have been corrected as your mentioned. And all the tables have been renumbered.

4. Line 105, Figure 3, It is very difficult to distinguish between the colours for the lines

corresponding to the side and center temperatures. Rather than colours, the two sets of

temperatures should be represented by a solid line and a broken line.

Re: Thank you for your correction. The two sets of temperatures have been corrected by a solid line and a broken line, respectively.

5. Line 128 and 129, “which is beneficial to improve gas permeability but improve charge reduction.” This phrase is confusing. Should “but” be “and”?

Re: Thank you for your correction. “but…” should be “instead of …”. That is, “which is beneficial to improve gas permeability instead of charge reduction”.

6. Line 134, “beneficia” should be “beneficial”

Re: Thank you for your correction. The word has been corrected as “beneficial”.

7. Line 137, Figure 4, The right-hand vertical axis has no identity!

Re: Thank you for your correction. The right-hand vertical axis of Figure 4 has been remarked.

8. Line 152, Figure 5. “Apparent softening viscosity with different CO2 ratio.” should be “Apparent softening viscosity and shrinkage with different CO2 ratio.”.

Re: Thank you for your correction. The figure title has been corrected as your mentioned.

9. Line 204, It is very difficult to read the scales on the vertical axis of the diagrams in

Figure16.

Re: Thank you for your correction. The figure16 has been pulled larger.

10. Lines 305-307. It can be found that with the increase of the reduction temperature, the content of TiO₂ and TFe in the samples increased by 1.31℃ and 4.91℃, respectively,” There is something wrong with this statement.

Re: Thank you for your correction. “℃” should be “wt.%”.

11. Line 321, Figure 17, It is unclear what the significance is of the different sub-figures. Are these at different temperatures? The printing is far too small to read.

Re: Thank you for your correction. The figure17 has been pulled larger.

12. Line 323, Figure 18, The right-hand vertical axis has no identity!

Re: Thank you for your correction. The right-hand vertical axis of Figure18 has been remarked.

13. In view of the limited significance of the findings expressed in this work, the Ms. is far too long. The text should be reduced by 50% and the number of figures reduced by about half.

Re: Thank you for your correction. In fact, the body content is about 4000 words, which is already very condensed. And the significance of the pictures listed in the article is to point out the future research direction. Thank you for your suggestion!

Round 2

Reviewer 5 Report

I note you have corrected the errors listed in the previous review.

However, there has been no reduction in the text or the number of figures, as requested in the original review.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 3

Reviewer 5 Report

Thank you for your good efforts in decreasing the number of figures and condensing the text by removing non-essential material. The modified Ms. is greatly improved.