Physical and Chemical Studies of Smelting Products of Calcinated Composite Pellets Produced from Chromium Production Waste

Round 1

Reviewer 1 Report

This environmental study deals with fine and effective treatment of techno-genic tailing waste product enriched with chromium (Cr2O3) compounds.

The melting of calcined compositional complex pellets was used. The mineral part refined product was used as flexing material, the fine coke for roasting of pellets and watery solution as binder.

The chemical- and physical-based approaches were used to study characteristics of these pellets from chromium-rich waste samples.

Remarks:

1 The first three paragraphs in introduction do need providing the references.

2 Please, in fourth paragraph, follow the upgrade citing the more recently published environmental study of chromium causing problem in watery phases.

 “The chromium-rich samples cause environmental burden and their analysis and characterisation is still a real challenge for scientists [https://pubs.rsc.org/en/content/articlelanding/2013/ay/c3ay40284c/unauth]. The chromium and ferrochromium application represents the smelting of alloyed steels, chromium bronzes and cast irons of special alloys.”

3 Provide a drawn scheme of the workflow used in this experimental pipeline. It is for the reader to quick comprehending the experimental design chosen in this work.

4 In conclusion, provide the future aims of the authors for further work in this scope of investigation.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files. 

Author Response File: Author Response.docx

Reviewer 2 Report

The content of this paper is generally OK and is probably of interest to people involved with the chromium industry. I had, however, some problems in trying to understand what the intended main message is. I will try to explain this in the following.

1) My expectations when I read a paper is that one or more "Research Question" (main purpose) is clearly presented early in the report, and that the Discussion and Conclusion provides answers to such questions. In between these two points a narrative should provide intermediate descriptions of "What" is done, "Why" things are done or choices made and of course also "How" this is done. My impression is that this paper is concentrated mostly on the "How", and I also find it hard to follow the narrative. 

The Abstract is too long and does not contain a research question and its answers.

2) The Introduction gives several possible research questions:

Lines 34-42 Solve problem of accumulated waste

Lines 47-50 Turning waste into a possible raw material for chromium and ferrochromium production. If it is true that "Production from mining waste is 2-4 times cheaper than from natural deposits" I would expect that this is done on a large scale.

Lines 114 - 119 Study the properties of smelting products

3) Pellets are made and subsequently reduced at high temperature as would be the procedure industrially. Here the pellets are crushed before the reduction. Would this make difficulties in using results from this work for industrial purposes?

4) A Tamman-furnace is used for the high temperature experiments, such furnaces can be horizontal or vertical and operated under vacuum or other pressures with or without possibilities for the generated gas to escape. A furnace sketch and some words on the gas atmosphere would be helpful.

5) I miss at least a small discussion of the process chemistry (main reactions, stability of alloy components etc.) and maybe also some words on the slag viscosity. Such things should be important background for choice of experimental temperatures. Here the temperatures are probably decided from information in references 30-33. But this is my guess. A discussion of this type could also give predictions about mass and composition of resulting phases in the experiments. Carbides in the alloy and possible entrapment of metallic droplets in the slag are obvious issues of importance.

6) Many tables are given containing a lot of information. In my mind the information given in Lines 198-200 could deserve a table too. Actually I would like to see a table of element mass balances for Cr, Fe, O and C for all four experiments. Main columns should be Input, Alloy, Slag and Gas.

7) The micrographs presented are worthless to me without instructions of what to look for. On Fig. 5 I assume the white spots are metallic droplets, but I might be wrong. The sample shown in Fig. 8 has the overall(?) composition as given in table 9, but what is what?

8) The Discussion and Conclusion does not address or answer directly any formulated research question. A statement like "The results suggest that the proposed charge in pellets allows for the reduction of chrome oxide to composite ferrochrome with a chrome content of 64.82 %" in Lines 355-356 makes me wonder. This is true for one of the experiments done here provided that the sampling and analysis are correct, however, in a conclusion of a research report/paper I would use a more modest number.

9) In Line 370 "GOSTs" are mentioned, besides being a pop group this is the Russian technology standards and should deserve a reference. This whole point 5 in the Conclusion also addresses "activity of sulfur" which has not been mentioned before, but could have been a matter in the discussion I mention in 5) above

10) Misprints occur in this manuscript as it does in many other, I will only mention a few:

Hyphens used wrongly: Line 26: "car-bide" should be "carbide" See also Lines 96, 125,149, 160, 207

Subscripts missing: Lines 60,80, 108, 124, 199, 200,

Should it be "RTF"AKTIKA" (Line 138) or "RTF ACTICA" (Line 145)? 

Line 309 "Table 9. ...", Line 323 "Table .9..." The second one is definately wrong.

There are sentences I do not understand the full meaning of here, but generally it is quite easy to understand the language. It might, however, be useful to let someone with a good knowledge of English read this and maybe suggest reformulations after discussion with the authors.

Try to think that you are telling a story with a beginning, a middle and an end.

Author Response

Thank you very much for taking the time to review this manuscript. Please find the detailed responses below and the corresponding revisions/corrections highlighted/in track changes in the re-submitted files. 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Authors have reacted to given queries

Reviewer 2 Report

Much better but there are always room for improvement, especially for the abstract. I think the sentence in lines 141 - 145: "The purpose of this work is to study the physicochemical properties of melting products of durable composite pellets obtained from technogenic waste of chromium production. In the manufacture of composite pellets inexpensive natural raw materials, such as ferruginous diatomites, as well as chromium production waste as a flux in the form of mineral part of refined ferrochromium slag, freed from metal corollas, were used." could in my mind replace most of the present abstract. I am although a bit dubious about if the words "diatomites" and "corollas" bear the exact meaning you intend.