Modes of Occurrence of Chromium and Their Thermal Stability in Low-Rank Coal Pyrolysis

Round 1

Reviewer 1 Report

General comments:

The goal

No information about main goal of research work carried out.

Is the research aimed at decrease the Cr emission from coal combustion/gasification ?

Are the authors looking for a method of coal cleaning?

If Yes, how authors want to do this?

Discussion on the results, in above context, is needed.

 

Detailed comments (selected):

42 Pyrolysis was an important initial step or intermediate process in coal combustion, gasification and liquefaction 

I think still is

45 However, only few literatures had studied release behavior of TTEs in coal during pyrolysis process

A  little bit "risky" sentence especially in case of mercury removing

48 holding time

I think: residence time will be better

126 .. to get rid of the moisture

Maybe: to remove the moisture

Total sulfur content in GL was obviously higher than NMH coal

Why is it so obvious? Maybe:... was much ; significantly higher

Fig. 3

Description under the drawing should clearly refer to all its parts (i.e. a and b) - this also applies to other drawings

I think the description of the legend is a bit misleading.

2. I think the description of the legend is a bit misleading.

e.g. the red bar is described as: HCL / HF extraction which suggests that the share of Cr bound to carbonate and aluminosilicate is 34.8%. This value in the text is assigned only to Cr bound to aluminosilicate. So in my opinion the red bar should be described as HF only (am I right or wrong?)

It would be nice if the authors will describe the methodology of thermodynamic calculations a bit more (Thermochemical equilibrium simulation)

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors should check the following:

Cl abbreviation

please add JCPDS card

how can you have obtained Quartz at only 250oC ? usualy is found after 500oC  at least, until then is amorphous silica,

be more explicit , why the coal contain Cl and why did you analyze it if you use it further for extraction of minerals ? : "Samples were crushed and then ground to pass through a 74μm mesh for Cr and Cl analysis. The guaranteed reagents for 100mg sample digestion were 6 ml HNO3, 3 ml  H2O2 and 3ml HF. and then you said In this study, HCl, HF, HNO3 and H2O2 were used to successively extract minerals  and organic matter from raw coals."

you repeat too often on some information 

the authors said "were pyrolyzed in a fixed-bed reactor from room temperature, at atmosphere pressure, with the heating rate of 5 °C/min, and the final pyrolysis temperature was from 400 to 800 °C with the interval of 100 °C." but at page 5 raw 197 they said : "Highly pure nitrogen (99.999%) was used to purge the crucible" , please correct to not be misunderstood.

 line 253 -Figure 3 where can i found H2O2 ?

figure 7 - please specify which is NMH and GL. ?

please explain better the TG data

use short sentences

EDX should be added to show what NMH and GL coal contain.

 

 

 

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear editor,

The authors improved the article by presenting additional data. I would also like to add that the authors answered almost all the questions, but I would like to mention that some information such as reference 11 is useless. What helps us to know about mercury if we talk about chromium. Before publication, I would like the authors to read and shorten the information to be presented as succinctly as possible. 

Author Response

Please see the attachment.

Author Response File: Author Response.docx