3D Printing Multi-Channel Large Volume Microchannel Reactor for Enhanced Removal of Low-Concentration NOx Flue Gas
Round 1
Reviewer 1 Report
The english language and writing has to be improved extensively. Literature review and backgroud introduction is not sufficient, for example withnot covering the recent development of gas-liquid microreactor, microchannel design and scale up (such as the design of the gas-liquid distributor for numbering up). Most importantly, the detail structure of the microreactor, expercially the gas-liquid mixing chammer and the distribution room is not shown clearly. The design rationale and consideration of the structure is not discussed. The porfmance of the distribtion room, i. e. the distribution uniformity of the two phase flow in the multi-channel is not presented. These imporatant information has to be added before the paper can be accepted.
Author Response
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Author Response File: 
Author Response.docx
Reviewer 2 Report
The authors manufactured a multi-channel large volume microchannel reactor by 3D printing to deal with the low concentration NOx flue gas.The topic is realistic and of high practical value in the increasingly urgent situation of pollution gas control.The paper makes full use of the advantages of simple, convenient and low cost of 3D printing technology to designed and manufactured the new reactor. The effects of number and length of channels, the concentration of (NH2)2CO and H2O2, the pH, the temperature and the gas flow rate on NOxremoval efficiency.Some meaningful results have been achieved. Here are some suggestions for the author:
1) The horizontal coordinate of figure 4 and figure6 is “contact time” in lines 239 and 290 in the statement of the effects of the concentration ofH2O2 and the temperature. However, when the flow rate is 150L/min, the “contact time” is constant according to the formula(2).Here the author needs to make more detailed explanation.In addition, it is mentioned in lines 305-307 that when the gas flow rate is 300L/min and 150L/min, the contact time is 3s and 9s respectively, while the contact time of lines 239 and 290 is in min, with a large gap between them.
2) According to the conclusion obtained in Section 2.4 of the paper, the increase of contact time leads to the increase of NOx removal rate, which is contrary to the trend shown in the figures of lines 239 and 290.
3) The surface roughness of the wall has a certain influence on the fluid flow in the microchannel, which is related to the selection of materials and precision of 3D printing. Although this is not an issue to be explored in this paper, it is suggested to briefly explain the materials and precision used.
4) Some statements have problems.
Line 47 "no" is not capitalized.
Line 264 "The NOx removal efficiency was 100%, and the NOx concentration in the exhaust gas was 0ppm." pH value is not specified.
Line 285 "... NOx the solubility of O2 and in the solution...",The original meaning of this sentence is" the solubility of O2 and NOx in the solution...".
The statement in line 296 is not smooth.
Author Response
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Author Response File: Author Response.docx
Reviewer 3 Report
NOx removal is undoubtedly a topic that deserves interest. The authors propose a method that considers NOx removal in the presence of urea and hydrogen peroxide at room temperature.
High temperature processes, as the ones described by the authors, produce nitrogen oxides that are far from being pure NO but a mixture that contains nitrogen oxides, oxygen, carbon oxides and sulphur oxides.
The proposed process must require to consider all these components that will affect NO solubility in water and will also affect the acid-base equilibria in solution and may induce urea decomposition. All this provided that exhaust gases temperature is reduced to 20ºC prior to reaction
On the other hand, it is known that acrylic and methacrylic esters of polyhydric alcohols oxidize through a radical chain mechanism with chain rupture. Therefore, aging studies of the process should be considered in order to determine the stability of the microchannel device.
These aspects must be addressed to publish this paper, moreover a comparative techno-economic analysis is suggested to analyze the viability of this process with respect to more conventional ones
Author Response
Please see the attachment.
Author Response File: Author Response.docx
