Towards a Mechanistic Understanding of the Slagging Propensities of Petroleum Coke: Lessons Learned from Its Co-Combustion with Natural Gas in Oxygen-Enriched Atmospheres

Round 1

Reviewer 1 Report

The relevance of the effective use of petroleum coke as a fuel for energy generation is debatable. However, this does not in any way reduce the relevance of research on the combustion of petroleum coke. In thith article a computational fluid dynamic study was carried out to compare the measured ash deposition rates on the outer surface associated with the combustion of petroleum coke (PK) – natural gas in AIR and O₂/CO₂ (70/30 vol.%, OXY70). The authors describe in sufficient detail the calculation methodology and the choice of boundary conditions. The reliability and scientific and practical value of the results obtained are beyond doubt. 

There are several points that I did not understand:

the authors in the article indicated that "A two- step mechanism where CO is first produced during devolatilization followed by its oxidation to CO₂ during the second reaction was employed to simulate the homogeneous gaseous combustion reactions". However, the authors did not specify which mechanism of homogeneous combustion was used. 

why in table 13, in "Primary burner species concentrations" in Column "Petcoke OXY70" note that O₂ concentration is 21 %_mol?

why is the "predictions line" not smooth on figure 3? These are calculated temperature values, so they do not have measurement errors. Shouldn't the calculated temperature change smoothly from distance from the burner?

In my opinion, in this article, the authors propose new effective approaches to calculating CFD and ash deposition rates, which may be useful for other researchers to calculate the combustion processes of emulsions and solid particles. 

Thanks to the Authors for an interesting scientific study. And sorry for my English.

Author Response

Thank you for your time and comments. Please see file attached. 

Author Response File: Author Response.pdf

Reviewer 2 Report

The main question addressed by the research is understanding the mechanism of  ash deposition behavior during petroleum coke  combustion.   The aim is to predict the ash deposition rate during petroleum coke  combustion, which is still not properly solved in published papers , while  it is relevant in this field of research related to technology of petroleum coke  combustion.
For the first time a Computation Fluid Dynamic study was carried out to match the measured outer ash deposition rates associated with the combustion of petroleum coke. The adequacy of the combustion models employed in the simulations was established. So the methodology applied is adequate.
Conclusions are proper addressing  the main question posed. The references are appropriate

Paper presents interesting and useful results, authors published several  articles in this field of research and their qualification is without doubts high. So paper can be accepted after minor revision. English is to be slightly polished, such as page 4, line 116 “ …the slagging and fouling propensities of PC is high…” etc.

Numbering of Figures and Tables is to be  ordered. Thus, Table 14 is  mentioned after Table 2, and Figure 6 before Fig. 1, etc.  

English is to be slightly polished, such as page 4, line 116 “ …the slagging and fouling propensities of PC is high…” etc

Author Response

Thank you for your time and comments. Please see file attached. 

Author Response File: Author Response.pdf

Reviewer 3 Report

1. The article conducted a detailed analysis using the CFD method, but there was less discussion on the accuracy analysis of the CFD method and the model used, including the independence of grid settings.

2.The conclusion section can be simplified, and some content can be included in the main text or listed as a separate section.

Minor editing should be made.

Author Response

Thank you for your time and comments. Please see file attached. 

Author Response File: Author Response.pdf