Effect of Return Fines Embedding on the Sintering Behaviour of Vanadium Titanium Magnetite Concentrates
, Hao Liu 1,*, Huangjie Hua 1, Zezheng Sun 1, Yuelin Qin 1, Fei Meng 1, Weiqiang Liu 2 and Guang Wang 3
Round 1
Reviewer 1 Report
Thank for the opportunity to review this manuscript. It reports a practical set of results useful in the guidance of preparation of raw material feeds to these sintering beds, however a number of questions arise from the experiments reported.
1. The experimental sintering pot is presumably of sufficient dimensions that perturbations such as channeling effects due to packing inhomogeneities etc. are minimal? This is important to state particularly with regard to the trials of impact of location of the returned fines in the sintering pot. It also presumably defines how sensitive the results reported are to the specific geometry of the sintering pot.
2. In figures 3 and 5, there is no evidence presented of the uncertainties associated with the data points. Presumably these numbers are based on single trials, in which case understanding the uncertainty of results particularly for the <1mm additions in figure 3 and the 20% ratio in figure 5 become quite important if trends are to be inferred. As just one example, the productivity curve in figure 5 suggests there is significant uncertainty associated with these measurements.
With regard to layout of the paper, a number of acronyms for unusual parameters are used (even in the introduction) such as TI and JPU before these terms are actually defined (which they are later in the experimental section).
Note: Lines 146-148 need to be deleted as they are from the text guide to authors.
Author Response
Title: Effect of Return Fines Embedding on the Sintering behaviour of Vanadium Titanium Magnetite Concentrates
Journal: Metals
Dear Sir/Madam,
First of all, the authors would like to thank the editor and the reviewers for their valuable comments and suggestions on the manuscript, which has significantly raised the quality of the manuscript. Below the comments of the reviewers are response point by point and the revisions are indicated. Thanks for all the help.
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Detailed Response to Reviewers
Reviewer: 1
- The experimental sintering pot is presumably of sufficient dimensions that perturbations such as channeling effects due to packing inhomogeneities etc. are minimal? This is important to state particularly with regard to the trials of impact of location of the returned fines in the sintering pot. It also presumably defines how sensitive the results reported are to the specific geometry of the sintering pot.
Response: The size of the sinter pot in the sintering experiment is 600 mm in height x 300 mm in internal diameter. Then we have always had the same people using the same tools at about the same time during each sinter pot loading. Please allow me to state some details about the experiments on the return fines embedding location. The first step is the granulation of the embedding and conventional granules separately and then the loading process are carried out according to the experimental scheme. A ruler is used to continuously measure the height of the charge during the loading process to ensure that it follows the experimental scheme.
- In figures 3 and 5, there is no evidence presented of the uncertainties associated with the data points. Presumably these numbers are based on single trials, in which case understanding the uncertainty of results particularly for the <1mm additions in figure 3 and the 20% ratio in figure 5 become quite important if trends are to be inferred. As just one example, the productivity curve in figure 5 suggests there is significant uncertainty associated with these measurements.
Response: The determination of the sintering indices mentioned in the paper is calculated according to equations 1-4. The parameters are related to each other, for example, productivity is controlled by yield and flame front speed, the higher the yield and the faster the flame front speed the higher the productivity would be.
Some discussions were added to the manuscript. There are two main reasons for the improvement in the permeability of the sinter packed bed. Firstly, with the implementation of the return fines embedding technology, voids are created around the large size return fines to improve the permeability of the sinter packed bed [24]. Then, during the usual granulation process, the large size return fines may crush the smaller granules, resulting in a deterioration of the granulation performance. The granulation performance is improved by the implementation of the return fines embed-ding technology.
During the granulation of the raw material, the returned fines will act as the central nucleus of the particles to bond the fines with water to generate granules. According to the blending ratio, a total of 28 kg of return fines was involved in the granulation. Compared to the base sample without returned fines embedding, 13.65kg of embedding was not involved in the granulation when the proportion of returned fines was 100%, resulting in a reduction of approximately 8% in the total mass of fines involved in granulation. This would result in a lack of the amount of central nucleus in the granulation process. The finer powders cannot be cemented into granules due to insufficient central nucleus, which finally leads to insufficient granules and further contributes to inferior granulation properties and sintering indices.
- With regard to layout of the paper, a number of acronyms for unusual parameters are used (even in the introduction) such as TI and JPU before these terms are actually defined (which they are later in the experimental section).
Response: The abbreviations in the abstract have all been changed to full name. The abbreviations in both the abstract and the introduction appear once.
- Note: Lines 146-148 need to be deleted as they are from the text guide to authors.
Response: Lines 146-148 in the manuscript have been deleted.
Reviewer 2 Report
This study attempt to investigate the influences of the particle size, mass ratio, and embedded location in the sinter pot of the RFE on the sintering behaviors such as productivity, yield, FFS, and permeability of VTM. After reviewing the manuscript, the reviewer thinks that this manuscript contains some useful information, however it requires clarification and additional information to support the conclusions. The followings are to be clarified.
1. It is recommended that all the abbreviation in the abstract should be described with its full name. Furthermore, it is advisable to notify abbreviation of RFE once in the abstract and introduction.
2. There are insufficient description of the mechanism of improving permeability in the manuscript. It is described that “In general, a higher FFS means a higher sinter bed permeability which is conductive to shorten the sintering time”. It is not the reason of the improving permeability of sinter packed bed.
3. In order to explain the effect of mass ratio exceed 80%, it is described that “the amount of central nucleus will be inadequate in the granulation process”. Is it experimental result or the referred from the literature? It is advisable to demonstrate the experimental result or the cited reference in the manuscript.
4. There are three experimental results of particle size distribution of VTM in Fig. 4, Fig. 6, and Fig. 9. What is the technical significance of these results, and it is advisable to discuss the each results in the manuscript.
5. There are incorrect references! For instance, [20] at line 144. It is advisable to recheck all the references.
6. There are incomplete sentences at line 144 ~ 148.
7. It is advisable to check the following section-numbering.
2.1 Raw materials
(1) Metallurgical Characterization of VTM Sinter
(2) Permeability
8. What is the upper limit of the return fines “(greater than 3 mm), which made to mix directly without granulation”, at line 190.
9. It is advisable to discuss the reason of the two major increments of permeability (JPU) resulted in Fig 10.
Comments for author File: 
Comments.pdf
Author Response
Title: Effect of Return Fines Embedding on the Sintering behaviour of Vanadium Titanium Magnetite Concentrates
Journal: Metals
Dear Sir/Madam,
First of all, the authors would like to thank the editor and the reviewers for their valuable comments and suggestions on the manuscript, which has significantly raised the quality of the manuscript. Below the comments of the reviewers are response point by point and the revisions are indicated. Thanks for all the help.
--------------------------------------------------------------------
Detailed Response to Reviewers
Reviewer: 2
- It is recommended that all the abbreviation in the abstract should be described with its full name. Furthermore, it is advisable to notify abbreviation of RFE once in the abstract and introduction.
Response: The abbreviations in the abstract have all been changed to full names. The abbreviations in both the abstract and the introduction appear once.
- There are insufficient description of the mechanism of improving permeability in the manuscript. It is described that “In general, a higher FFS means a higher sinter bed permeability which is conductive to shorten the sintering time”. It is not the reason of the improving permeability of sinter packed bed.
Response: The manuscript has been changed to: There are two main reasons for the improvement in the permeability of the sinter packed bed. Firstly, with the implementation of the return fines embedding technology, voids are created around the large size return fines to improve the permeability of the sinter packed bed [24]. Then, during the usual granulation process, the large size return fines may crush the smaller granules, resulting in a deterioration of the granulation performance. The granulation performance is improved by the implementation of the return fines embed-ding technology.
- In order to explain the effect of mass ratio exceed 80%, it is described that “the amount of central nucleus will be inadequate in the granulation process”. Is it experimental result or the referred from the literature? It is advisable to demonstrate the experimental result or the cited reference in the manuscript.
Response: The manuscript has been changed to: According to the blending ratio, a total of 28 kg of return fines was involved in the granulation. Compared to the base sample without returned fines embedding, 13.65kg of embedding was not involved in the granulation when the proportion of returned fines was 100%, resulting in a reduction of approximately 8% in the total mass of fines involved in granulation. This would result in a lack of the amount of central nucleus in the granulation process. The finer powders cannot be cemented into granules due to insufficient central nucleus, which finally leads to insufficient granules and further contributes to inferior granulation properties and sintering indices.
- There are three experimental results of particle size distribution of VTM in Fig. 4, Fig. 6, and Fig. 9. What is the technical significance of these results, and it is advisable to discuss the each results in the manuscript
Response: The manuscript has been changed to: As shown in Figure 4, the size of the return fines for embedding had little effect on the size distribution of the vanadium and titanium sinter. However, at return fines for embedding size less than 1mm, the largest proportion of sinter size is less than 10 and therefore the lowest yield is achieved, consistent with that mentioned previously.
As shown in Figure 6, the size of the return fines used for embedding has a considerable effect on the size distribution of the VTM sinter. At a 20% embedding mass ratio, the smallest proportion of sinter larger than 10mm and the largest proportion of sinter smaller than 10mm are found. At an 80% embedding mass ratio, the size distribution of sinter is greatest for 16-25 mm and smallest for sizes less than 10 mm.
As shown in Figure 9, the location of the return fines used for embedding had practically no influence on the size distribution of the VTM sinter.
- There are incorrect references! For instance, [20] at line 144. It is advisable to recheck all the references.
Response: This is indeed a bibliographic error and the manuscript has been changed to Japanese permeability units (JPU) [26].
- There are incomplete sentences at line 144 ~ 148.
Response: The manuscript has been changed to: The permeability of the wet granular packed bed was measured in Japanese permeability units (JPU) [26]. The sintering mixture permeability was determined according to the Voice formula.
- It is advisable to check the following section-numbering.
2.1 Raw materials
(1) Metallurgical Characterization of VTM Sinter
(2) Permeability
Response: The manuscript has been changed to:
2.1. Raw materials
2.2 Metallurgical Characterization of VTM Sinter
2.3 Permeability
- What is the upper limit of the return fines “(greater than 3 mm), which made to mix directly without granulation”, at line 190.
Response: In fact, this manuscript refers to return fines with a particle size of less than 10mm. So the particle size ranges for the line 190 inlay are less than 1mm, 1 to 3mm, 3 to 5mm, 5 to 7mm and 7 to 10mm respectively.
- It is advisable to discuss the reason of the two major increments of permeability (JPU) resulted in Fig 10.
Response: The manuscript has been changed to:
During the sintering process of VTM, the permeability of the sinter packed bed undergoes two major increases. The increase in the permeability of the sinter packed bed for the first time was due to the fact that the negative pressure at the ignition was 8kp and after the ignition, the negative sinter pressure increased to 15kp. As the negative pressure increased the airflow through the sinter pots also increased and the permeability of the sinter packed bed was increased according to equation 5. Then, the permeability remains in a relatively stable condition until the sintering reaches the later stage. At this stage, the permeability raises rapidly and reaches the peak near the termination of sintering.
Reviewer 3 Report
The study concerns the effective use of low- grade iron bearing minerals, namely, the optimization of the permeability of the sinter packed bed using various returned fines regimes and products. The authors demonstrate a beneficial effect on the sintering process and product from the size of the returned fines, the proportion and the locations of embedded return fine layer. The work is well structured, provided with drawings and diagrams to help achieve understanding. The topic is relevant in view of the economic and environmental challenges facing metallurgy. Since progress towards these goals is demonstrated here, I consider the work worthy of acceptance.
A little note: check the citation format. For example, Zhu et al.[21] and MATSUMURA et al. [26]. It needs to be unified.
Author Response
Title: Effect of Return Fines Embedding on the Sintering behaviour of Vanadium Titanium Magnetite Concentrates
Journal: Metals
Dear Sir/Madam,
First of all, the authors would like to thank the editor and the reviewers for their valuable comments and suggestions on the manuscript, which has significantly raised the quality of the manuscript. Below the comments of the reviewers are response point by point and the revisions are indicated. Thanks for all the help.
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Detailed Response to Reviewers
Reviewer: 3
- check the citation format. For example, Zhu et al.[21] and MATSUMURA et al. [26]. It needs to be unified.
Response: Thank you for your suggestion, the original has been changed to Zhu et al.[21] and MATSUMURA et al.[26].
Round 2
Reviewer 2 Report
Accept in present form
