Research on Co-Combustion Behaviors of Binary and Ternary Blends of Coal, Walnut Shell, and Biochar by TGA

Round 1

Reviewer 1 Report

The article presents an experimental study of the combustion behavior of binary and ternary mixtures based on lignite, biochar and walnut shell. Thermal transformation was studied using thermogravimetry. The results are compared with the combustion behavior of the individual components in search of synergy. The authors gave a description of the influence of active radicals in the catalytic and inhibitory effects of the interaction. The article is quite valuable, but needs to be improved.

Line 40 “The research and application of biochar is an emerging field.” This is a rather controversial statement. Biochar is being researched and used quite extensively as well as with coal. Please consider correcting this statement.

Line 85. The authors indicate that a few studies there are on the co-utilization of biochar and coal but do not review any particular results. Please, consider adding a deeper analysis of previous achievements in this direction and, possibly, in adjacent ones. In general, the novelty and significance of the research are not highlighted clearly in Introduction.

Table 1. Please indicate the basis for the parameters analyzed.

Line 112. Please indicate the model and basic characteristics of the analyzer.

Please provide the reasons for the experimental conditions chosen, including the ratio of oxygen to carbon dioxide.

The influence of diffusion processes on the combustion of individual components, binary and ternary mixtures, was practically not discussed in the article. Please consider this question.

Figure 4. Please provide further comments on whether it is fair to consider the shift of the experimental and theoretical curve to be significant on the scale of future co-combustion processes.

How do the heating rates used in the experiments compare with the heating rates in the process reactor or boiler? Please provide such comments to increase the value of the results for thermal power engineers.

The finalizing statements on the kinetic analysis are not presented in Conclusions.

Please, emphasize the connection of the study with the journal’s scope, for instance, highlighting the connection of the results with possible processes of energy system planning and energy technologies.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

In this work, the effect of biochar and walnut shell on the coal combustion was investigated by means of TG analysis. The work is well written and organized, the sections are well described and the readiness is very good.

In order to improve the quality of the work, I would suggest some integrations:

·         The “synergistic effects” or more simply the deviation from the theoretical trends in TGA curves are very slight but present. It would be very useful and interesting if the produced gases could be analysed for example by means of FTIR analysis as reported in doi: 10.3390/app112311188. In such way, the synergistic effect can be understood.

·         In the same work, the evaluation of hemicellulose, cellulose and lignin starting from TGA curves was performed by using the Frazer-Suzuki deconvolution. I would suggest to the authors to perform the same evaluation.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf