End of Life Tires as a Possible Source of Toxic Substances Emission in the Process of Combustion
Round 1
Reviewer 1 Report
The paper was greatly improved; most of the referee suggestion were accepted and integrated in the text. However, I still disagree with the conclusion that are not completely supported by the adopted experimentation methodology. In fact, two aspects are not taken into consideration: the fluidodinamic of the calorimetric chamber, and the kinetic aspects. In the experimentation a constant flow of air is used during combustion, but this probably is not sufficient to assure the right turbolence inside the chamber and then a a well mixing of oxygen with pyrolysis products. Probably a parametric study with different air flow rate or different amount of oxygen could overcome this aspect. The second aspect is intrinsic with the methodology. Using a calorimetry the gas are released gradually and combusted al the temperature they are released, but, in real life, the combustion takes place in an environment that is at much higher temperature than that of this experimentation, and this entails much higher reaction kinetics then that can be experienced in a calorimetic experiment.
I therefore believe that before accepting the paper it is necessary to clearly highlight the l limits of the experimentation or as an alternative modify the conclusions
Author Response
Dear Reviewer!
Thank you for your review and comments. You recommendations were very useful and were accepted. The text was added with discussion of real conditions of combustion in compare with the experiments; the corresponding modification of the conclusions was made.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The subject of the thesis is interesting, but the manuscript requires significant corrections in its current form, it is not suitable for publication.
Comments:
-The introduction is too short lack of reference to the latest global publications.
-There is no specific paper aim.
- Is the proposed technology economically justified?
- What are the legal regulations regarding gas treatment and standards for this type of pyrolysis
- No precisely characteristics of the material used
- It could be characterized by the FTIR spectroscopic method
The article contains many wrong phrases such as:
- differential thermogravimetric analysis (DTG) should be Derivative thermogravimetry (DTG)
- What means "condensed to produce pyrolysis fuel" page 3, verse 80, it should be explain
- What means "thermal destruction of the polymer composition" page 3, verse 97, it should be explain
- "The total calorific value" page 4, verse 130, this is an incorrect definition of this value
Author Response
Dear Reviewer!
Thank you for your review and comments. You recommendations were very useful and were mainly accepted.
I would like to response point-by-point to your comments.
-The introduction is too short lack of reference to the latest global publications.
Accepted. The references to the latest global publications were added and introduction was extended.
-There is no specific paper aim.
Accepted. The paper aim was added to the introduction.
- Is the proposed technology economically justified?
The article is about the hazard of ELT in burning process, not about the technology. Only a specific technology, not a process, can be economically justified.
- What are the legal regulations regarding gas treatment and standards for this type of pyrolysis
Accepted and added
- No precisely characteristics of the material used
The characteristics of used ELT and experimental conditions are described in the section “Materials and Methods”
- It could be characterized by the FTIR spectroscopic method
The researching of ELT by fourier-transform infrared spectroscopy (FTIR) was not the purpose of this article
The article contains many wrong phrases such as:
- differential thermogravimetric analysis (DTG) should be Derivative thermogravimetry (DTG)
Accepted and corrected
- What means "condensed to produce pyrolysis fuel" page 3, verse 80, it should be explain
Accepted and added
- What means "thermal destruction of the polymer composition" page 3, verse 97, it should be explain
Accepted and added
- "The total calorific value" page 4, verse 130, this is an incorrect definition of this value
Accepted and corrected
Author Response File: Author Response.pdf
Reviewer 3 Report
First of all, the idea of the submitted paper is interesting. In the submitted paper, in Introduction section authors have showed relevant literature regarding the topic of this paper. But to the average reader it is not clear what authors intended with this introduction, what is the main goal of this manuscript. Likewise, language and grammar is not at expected level, need to address this problem. There are many presented facts that are not confirmed with relevant literature. For example: line 55-56. In the section Materials and Methods some data are missing, for example: line 62 and 64 (city, manufacturer?).
In the Result section authors showed the result of the TG and DSC analysis. Fig. 1 is too messy; authors are advised to divide it to the two figures, maybe first one showing just TG and second one showing DTG. It is difficult to distinguish the peaks and curves. Likewise, in line 88 authors stated that “The mass drop has two main distinct areas.” In practice it is commonly to write mass loss. As well, by detailed examination of the Fig. 1 one can notice more than two areas, we can call them peaks. Hence, there are two peaks in inert and four peaks in air atmosphere. Why these peaks are not addressed in the Discussion part? In Fig. 3 there are also some peaks that are not mentioned in the Result and Discussion. In lines 134 and 135 authors write total calorific value in MJ/kg, while on the Fig. 3 there are expressed in J/g. Please uniform this. Likewise, in Result part there are showed results of the gases mass spectrum analysis. It is always good idea to see what the products of the TG degradation are. In line 154 authors stated the “Pyrolysis fuel probably contains some other toxic compounds that were not discovered in our investigation…” If you don’t know, not sure, or don’t have relevant literature to support this fact it is better not to write it like this.
When you read the Discussion section, one can gain an impression that this is actually an Introduction section. All in all the whole Discussion section is consisted from too many sentences and conclusions made by other authors. What about conclusions that can be drawn from this investigation?
Finally, there is the Conclusions section. This section is totally different from the rest of the manuscript as if they were written by other authors. After reading the conclusions, reader can finally get an impression what authors wanted to achieve with this investigation. Authors are advised to deeply reformulate the Result and Discussion sections so they can be connected with Conclusion part.
For future investigation authors are advised to perform TG analysis of the investigated samples at least four different heating rates in inert and air, and from these data calculate the average apparent activation energies (follow ICTAC Kinetics Committee recommendations for performing kinetic computations on thermal analysis data (Thermochimica Acta 520 (2011) 1–19 and Thermochimica Acta 590 (2014) 1–23)). After that authors will have good starting point to find a model and kinetic parameter values coherent with the TG/DTG curves, and finally to reveal the mechanism of thermal degradation. Along with this results of the gases mass spectrum analysis that would be one excellent starting point for better understanding of this ELT problem. Likewise, authors are encouraged to perform TG/FTIR measurements if possible. This will bring more useful data.
Author Response
Dear Reviewer!
Thank you for your review and comments. You recommendations were very useful and were mainly accepted.
I would like to response point-by-point to your comments.
- But to the average reader it is not clear what authors intended with this introduction, what is the main goal of this manuscript.
Accepted. The manuscript goal was added to the introduction.
- Likewise, language and grammar is not at expected level, need to address this problem.
The professional linguist have corrected the new version of the text.
- There are many presented facts that are not confirmed with relevant literature. For example: line 55-56. In the section Materials and Methods some data are missing, for example: line 62 and 64 (city, manufacturer?).
The corresponded information and references were added.
- In the Result section authors showed the result of the TG and DSC analysis. Fig. 1 is too messy; authors are advised to divide it to the two figures, maybe first one showing just TG and second one showing DTG. It is difficult to distinguish the peaks and curves.
We think that the separation of curves to two figures would be lower informatics because the one curve is added by another one.
- Likewise, in line 88 authors stated that “The mass drop has two main distinct areas.” In practice it is commonly to write mass loss.
Accepted and corrected.
- As well, by detailed examination of the Fig. 1 one can notice more than two areas, we can call them peaks. Hence, there are two peaks in inert and four peaks in air atmosphere. Why these peaks are not addressed in the Discussion part? In Fig. 3 there are also some peaks that are not mentioned in the Result and Discussion.
We consider that thermal decomposition of ELT is due to pyrolysis of numerous individual compounds. The bends (shoulders) observed on the curves are associated with formation and removing of these compounds or groups of such compounds. We found it possible not to discuss the phenomenon of their appearance due to the small effect of these bends. However, the curves (TG, DTG, DSC) show clearly expressed two areas which we associate with the decomposition of the original composition to pyrocarbon and the oxidation of pyrocarbon to carbon oxides in the presence of oxygen. The presence of these two areas is not in doubt and is confirmed by the literature data. Therefore, we found it possible to limit the description with two main and explicit steps of heat treatment.
- In lines 134 and 135 authors write total calorific value in MJ/kg, while on the Fig. 3 there are expressed in J/g. Please uniform this.
Accepted and corrected
- Likewise, in Result part there are showed results of the gases mass spectrum analysis. It is always good idea to see what the products of the TG degradation are. In line 154 authors stated the “Pyrolysis fuel probably contains some other toxic compounds that were not discovered in our investigation…” If you don’t know, not sure, or don’t have relevant literature to support this fact it is better not to write it like this.
Accepted and corrected.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The Authors have addressed all the reviewers comments. After revisions, the quality of the manuscript has been adequately enhanced. Therefore, the manuscript is now suitable for publication in the Journal.
Author Response
Dear Review!
Thank you for your review and comments. You recommendations were very useful and helped to make the manuscript much more quality and reasonable.
Reviewer 2 Report
Authors still should carefully check English nomenclature and definition.
Author Response
Dear Review!
Thank you for your review and comments. You recommendations were very useful and helped to make the manuscript much more quality and reasonable. The article was checked by a professional English linguistю
Reviewer 3 Report
after reading the new version of manuscript entitled: End of Life Tires as a Possible Source of Toxic Substances Emission in the Process of Combustion, by authors: Irina Glushankova, Aleksandr Ketov, Marina Krasnovskikh, Larisa Rudakova, Iakov Vaisman I can confirm that the manuscript has been significantly improved and now can be published in Resources.Author Response
Dear Review!
Thank you for your review and comments. You recommendations were very useful and helped to make the manuscript much more quality and reasonable.
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Object of the paper is the study of products obtained from the energy valorization of end of life tires. The study is conducted in a small scale using termogravimetric analysis, the results are originals and interesting, but the conclusion are not completely supported by the data. Also some aspects of the experimental procedure need to be better clarified before publication.
It is necessary to better detail the analytical conditions, in particular it is necessary to specify the rate of the air used in the combustion experiment. Furthermore, although it is almost obvious the formation of cyanide compounds and cyanogen during pyrolysis (in the presence of carbon, nitrogen and hydrogen and a source of energy, it is highly probable the formation of toxic cyano compounds), it is not the same if the oxidation products are considered. In fact, during oxidation cyano compouds, are generally readily oxidized to more stable compounds (cyanogen and cyanides are endothermic very reactive compounds). The presence of cyanogen is then due to incomplete oxidation that could be the effect of a deficiency of oxygen or due to bad mixing also the low temperatures can produce incomplete combustion. On the basis of the used experimental procedure and equipment, the only conclusion that can be drawn is that there is formation of hydrocyanic acid during the pyrolysis step, that in the used experimental conditions it is not completely oxidized.
it is no coincidence that the current European legislation on waste incineration require that the gas remain at least for two second at a temperature higher than 800°C.
Reviewer 2 Report
The present study is based on the use of calorimetric analysis techniques (TGA, DTA and DSC) coupled with a mass analyzer (quadrupole) to establish the nature of the gases produced under atmospheres of air or inert. Work does not bring anything new to scientific knowledge. There are many works that have studied this same topic, with greater precision and more material means. I have not found in the manuscript anything that was of interest or that I did not previously know. Consequently, the manuscript should be rejected.
Reviewer 3 Report
The novelty of the study does not appear clearly.
The presentation lacks of precision on many crucial points.
Comments for author File: Comments.pdf
