CO₂ Capture and Crystallization of ATH Using Sodium Aluminate Solution in a Bubble Column Scrubber

Round 1

Reviewer 1 Report

The work submitted to Energies by Pao Chi Chen et al is interesting, although not fully new. The use of the continuous bubble column scrubber filled with sodium aluminate alkaline solution for capturing CO2 can be considered positive elements in this study. Also, the influence of five variables, including solution flow rate (A), concentration of the solution (B), gas flow rate(C), CO2 gas concentration (D) and liquid temperature (E), were explored in this study. The result of Taguchi analysis showed that overall order of importance is D>A=B>C>E. I think that this manuscript may be published in the Energies. However, some experimental analysis must be corrected or modified.

• Scherrer equation is for calculating crystalline size, not particle size. The crystalline size calculated from Scherrer equation in Table 8 is not corresponded to the particle size observed in SEM images in Figure 9. The author should use different terms of crystalline, grain, and particle sizes.
• Particle size should be observed in SEM or TEM images by measuring et least 100 particles for each sample.
• I have a recommendation to give a rare economic analysis of this process by considering operating and raw material costs.
• The author should include recent researches in the introduction section. Only couple of papers published in 2020 and 2019 are mentioned in this section.
• Resolutions of Figures 7, 8, 9, 10, and 11 are too low to be observed.
• There are also rare misprints in the text.

Author Response

Please see attached.

Author Response File: Author Response.pdf

Reviewer 2 Report

This paper is very interesting and has novelty. Authors have done a very good work. Nonetheless, I have two concerns with this work, which must be addressed prior publication. Please follow my comments below:

• The Introduction does not justify with enough literature the different alternatives for carbon capture and utilization. This is important for the reader to evaluate the novelty of your work. Therefore, a major change is needed here.
• The methodology is not well explained. Following the methodology, I would expect 32 experiments instead 16, and this is mainly because is not well detailed. Please, re-write the methodology section accordingly.

Good work and thanks.

Author Response

Please see attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

Review of the article:

  CO2 capture and crystallization of ATH using sodium aluminate solution in a bubble column scrubber

Authors:

Pao Chi Chen, Shiun Huang Zhuo and Jyun-Hong Jhuang

The topic of the paper refers to an experimental study that was conducted in order to investigate

the capture of CO₂ in a continuous bubble column scrubber using sodium aluminate alkaline solution. Aluminum tri-hydrate (ATH) precipitates was produced. The sodium carbonate could be recycled after the filtrated solution was crystallized by evaporation.

Generally, the manuscript is very interesting, the experimental procedures were well designed and the article is correctly written. Paper could be accepted for publication after a minor revision, taking into account the following suggestions:

Lines: 59-62

CO₂ can be used as a raw material to synthesize methanol, and can also be used as a raw material and captured by seawater to become a carbon source for cultivating seaweeds. All these are a part of CCU. However, the methanol synthesis technique remains to be broken through.- Lack of references for this affirmation

Lines: 68-70

The ATH mainly acts as an environmentally friendly flame retardant and in other applications, and it can also be used as a water conditioning agent and in toothpaste, and it is an antiacid. – consider revising

Line 89 : as α1 in the figure – which figure?

Line 90 : as α2 in the figure – which figure?

Lines 196-197

Table 1 shows the factors and levels of design of experiments, there are five factors with four levels for each factor. - consider revising

Lines 203-205

B is the concentration of NaAlO₂, determined by the operating range in literature, which is 1-3 M;- Which literature?

Both C and D were determined according to prior experience of this laboratory and some document information. ;- Which literature?

Line: 218:  was actuated - consider revising

Line: 257:  for heat evaporation- HOW? Evaporation is related to a liquid-gaz phase NOT heat. - consider revising

Lines: 259-260:

the volume of evaporated water was recorded after the operation. It required evaporation of the solution, and the heating was stopped at least 2 hours - consider revising – because the water was already evaporated

Lines: 275-276:

No.1 is identified as steady-state operation, which is the criterion of steady-state operation in the other experiments – Which experiments?

steady-state or steady state – you have to choose among them 

Line 445:

the solvent was evaporated by evaporation- consider revising

MANDATORRY: Grammar and spelling revising

Author Response

Please see attached.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Thanks for addressing my comments.