Influence of Compound Additives on Sulfur Fixing Performance of Sorbent Based on Steel Slag at High Temperatures

Round 1

Reviewer 1 Report

The presented manuscript is very interesting, as it solves two problems at once - slag utilization and decrease of sulfur dioxide emissions during coal combustion.

But there are a number of remarks about the manuscript:

1) It is necessary to clarify the title of the manuscript. In its current version, it indicates an improvement in the composition of the slag from steelmaking, rather than the reuse of slag for the disposal of SO2 emissions.

2) Why were these additives chosen?

2.1. Additives of sodium lignosulfonate will saturate the slag with additional sulfur. Why its need?

2.2. Why were NaCl and KNO3 chosen rather than carbonates or oxides of sodium and potassium?

3) NaCl and KNO3 will add chlorine and nitrogen dioxide emissions when decomposed at high temperatures. Have you measured their concentration in flue gases?

4) Table 2. Where does Ag2O come from in the composition of steelmaking slag? Recheck the result.

5) Figure 2. The effectiveness of sodium lignosulfonate supplementation increases with increasing its concentration. Is this due to its decomposition and the introduction of additional sulfur into the slag?

6) Table 4. Consider presenting it as an experiment design matrix. It seems to me that it will be more beautiful and presentable.

7) Does the size of slag powder affect its ability to absorb SO2? Have these studies been carried out?

8) According to formulas (2)–(3), sulfur combines into calcium sulfates, however, no sulfates were found on Figure 3. Why?

9) Have similar studies been carried out by other authors? What slag compositions did they have and what additives were introduced?

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This study is focused on reducing sulfur emissions during coal combustion by co-injecting modified steel slag. The authors used a suite of techniques to measure the amount of sulfur captured by the steel slag, as well as to characterize and optimize the steel slag. The topic is of interest. It isn’t clear what advantages this approach may have over conventional flue gas desulphurization techniques. The biggest weakness of this study is that some of the statements aren’t supported by experimental results and should therefore be restated as hypotheses, or, ideally, supported by additional experimental work. SEM results in particular are unconvincing. Language should be revised throughout the manuscript. Additional comments are provided with the attached document.

Comments for author File: Comments.pdf

Author Response

Thank you so much for your insightful remarks. I should have thoroughly revised it in the first draft.

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper presents investigation that is interesting from research  and practical point of view. The content is well presented and supported by robust state of the are with more than 30 publications on reference list. Only minor corrections are required:

- on Figure 1 the numbers are difficult to read;

- Tables 2 and 5 should be rearrange;

- the figures numbering should be reviewed;

- it would be valuable to extend the conclusions.

  

Author Response

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Author Response File: Author Response.docx

Reviewer 4 Report

In this manuscript, the authors used steel slag as the sulfur-fixing agent and report the positive effects of the steel slag additives on the high-temperature sulfur-fixing performance. In their work, the ideal steel slag Ca-S ratio was explored to be 2.5, and it was found that an optimal additive combination with a maximum sulfur fixing efficiency of 70.81%. This work is interesting but the manuscript was poorly written. I recommend the publication of this manuscript only after the major revision on the issues listed below.

 

1)  In Fig.1, why the Ca-S molar ratio of 2.5 was chosen in your experiment? The given explanation looks not reliable enough. Put some references if possible.

2)  In Fig.3, the peaks locate at 62.5 degree indicate different phase (fig.3c, fig.3d)?

3)  The English writing must be improved to make everything clear.

4)  There are too many typos in the manuscript that must be corrected: line 81, 82, 86, 111, 112, etc.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

1)      It seems to me that it is worth adding the phrase "sorbent based on steel slag" to the title: “Influence of Compound Additives on Sulfur Fixing Performance of Sorbent Based on Steel Slag at High Temperatures”

2)      What additives do you plan to replace sodium lignosulfonate in your future research?

3)      What production was the slag taken from? Because the content of silver oxide in this slag is so high that it can be sent for processing to extract silver. In our region, a mining and processing complex was recently built where there is much less silver in ore ...

4)      An experiment design matrix is usually built in order not to sort through the concentrations of a large number of input elements, since experimentally this can lead to millions of samples under study. It is a pity that you do not own this technique, it is worth learning.

5)      The use of self-disintegrating calcium silicate slags as sorbents is being studied by a number of other authors. In particular, you can familiarize yourself with the method of manufacturing granular sorbents (I think it will be useful to you) in the following works:

“Utilization of metallurgical slag with presence of novel CaO-MgO-SiO2-Al2O3 as a composite sorbent for wastewater treatment contaminated by cerium”. Journal of Cleaner Production, 2020, 255, 120286.

“Insights into sorption–mineralization mechanism for sustainable granular composite of mgo-cao-al2o3-sio2-co2 based on nanosized adsorption centers and its effect on aqueous cu(Ii) removal”. Nanomaterials, 2022, 12(1), 116.

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Unfortunately, the authors did not address my main concerns, again highlighted in the attached revised manuscript.

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Round 3

Reviewer 2 Report

The authors have addressed most of my remaining comments.