Specifics of Electrostatic Precipitation of Fly Ash from Small-Scale Fossil Fuel Combustion

REVIEWER #1

The manuscript provides the optimal operational parameters of a honeycomb type electrostatic precipitator cleaning flue gases from coal-fired medium-scale boiler. The manuscript is original and of practical importance for electrostatic precipitators users and designers, and can be interesting for the journal readers. English is satisfactory in general, but some sentences, grammar and wording needs improvement, for example, "further" should be replaced with "the following", "initial voltage" (probably) the "corona onset voltage", "gas flow" should be specified "gas flow rate/velocity", "figured" > "shown", "numerical concentration" > "number concentration", "volt-amphere > "current-voltage", "accepted.. " > "assumed to be..", "Follow technological parameters..."> "The following technological parameters..".

Reviewer comments and suggestions

Authors reply

1

Line 121. " 2.25 to 5.6 " please provide reference.

The Authors used fly ash dielectric parameters from Russian-language sources, such as [1]. English-language works, such as  [2], state the dielectric constant value of 2.1-3.06 for coal ash. Another work [3] investigates the dependence of the dielectric parameters of ash on the chemical composition and asserts the dielectric constant value for the studied lignite samples in the range of 2.9-3.7. in work [4], the measured dielectric constant values are presented in a range similar to that given in our work; the constant prediction method respecting the fly ash chemical composition is also presented, and corresponding calculations can confirm the values given by us. In our improvement manuscript, we do not discuss this issue to avoid littering the work, but we provide a relevant citations consecutively (Please see line 117).

2

Line 142. The secondary emission mechanisms due to back-corona discharge was recently studied by Krupa et al. Powder Technology 344 (2019) 475–486, indicating the dust eruption.

We believe the results of the referenced work are important and are therefore cited in our improved manuscript (Please see lines 137 and 138).

3

Table 2. Explain symbols W and A resulting from the CHNSO analysis.

Table 2 is corrected.

4

Line 238. Be specific what is the length of "45 mm"? Is it an inradius or circumradius, or side length? Show this dimension exactly in Figure 2. Line 348: Please indicate also the distance R at the scheme in Figure 2. Is it perpendicular to the hexagon side?

The design of the electrostatic precipitator involves honeycomb collecting electrodes with a hexagon side length of 45 mm, which corresponds to the radius of the circumscribed circle.

The distance between the electrodes R was measured in the direction perpendicular to the hexagon side and corresponded to the inscribed circle radius. This distance was used when the field in the honeycomb cell was approximated to a wire-to-cylinder electrode system. Katsov confirmed the inaccuracy of such an approximation as acceptable for engineering practice [5].

Figure 2 is updated.

5

Line 250. Was the supply voltage off during rapping of discharge electrodes to avoid breakdown/short circuit? Explain.

The electrodes were regenerated on a switched-off ESP after every single experiment. Rapping of the discharge and collecting electrodes was not required during measurements since the current and voltage values in the ESP were stable: obviously, dust collected on the electrode surface did not affect the electrical parameters. Please see lines 333-337.

The sparking and short circuits during the regeneration of discharge electrodes is a rather complex issue and requires special studies.

6

Line 349. The mobility of 2.1x10-4 m2/Vs is for normal conditions (Cobine, Gaseous Conductors). This value has to be recalculate to a temperature specific for electrostatic precipitator.

For precise physical science experiments, ion mobility should be surely evaluated respecting the gas temperature. However, we believe that using the mobility value for normal conditions introduces inaccuracy, which is acceptable for practical engineering and is much lower than the error introduced by approximations when calculating particle charges.

7

References. Missing journal or conference data, or webpage address in some references.

The references were improved

REVIEWER #2

The manuscript titled " Specifics of Electrostatic Precipitation of Fly Ash From Small-Scale Fossil Fuel Combustions" investigates the removal efficiency of the honeycomb electrostatic precipitator (ESP) applied to control the particulate matter (PM) emissions from the small-scale boiler with combustion lignite and hard coal. The overall methodology and manuscript are poorly written—many spelling and typo mistakes. The experiment description and results description are brief, whereas the introduction is quite long. I would recommend that the author should correct and submit it again.

Reviewer comments and suggestions

Authors reply

1

The spelling of the filter in Fig. 1 is needed to be corrected.

Figure 1 is corrected.

2

The explanation of the experimental setup should be increased.

Authors prefer concise texts and realise that

that the Introduction volume has been increased. Information on the electrostatic precipitation basics, the properties of fly ash, and related processes such as reverse corona or nucleation is approximately 800 words. Since our work is intended for a wide range of readers related to engineering, we consider this information necessary and provide it in a minimal volume, supplemented with references to more detailed information. In addition, we believe such an expanded Introduction to be reasonable since it avoids a new chapter and, therefore, reformulation.

We have tried to consistently describe the experimental setup measurement equipment and sampling technics, providing only the necessary information and introducing citations for details. We believe that this part of the manuscript contains all the information necessary to experiment replication and supports the discussion and argumentation of the correctness of the conclusions.

3

The results and discussion parts should be elaborated more, and the results should be compared with the latest research work; most references cited are quite old.

The result and discussion section is improved, please see lines 33-337 and 355-360. Referents have been replaced with newer ones wherever possible. However, some cited references are still actual and can be replaced, e.g. fundamental works of Deutsch [6] and White [7].

4

The equation numbers are not mentioned in the text.

The manuscript was improved. Please see lines 341,358-360 and 416.

5

Subscript mistakes in the text.

Subscripts were corrected all over the manuscript.

REVIEWER #1

The manuscript provides the optimal operational parameters of a honeycomb type electrostatic precipitator cleaning flue gases from coal-fired medium-scale boiler. The manuscript is original and of practical importance for electrostatic precipitators users and designers, and can be interesting for the journal readers. English is satisfactory in general, but some sentences, grammar and wording needs improvement, for example, "further" should be replaced with "the following", "initial voltage" (probably) the "corona onset voltage", "gas flow" should be specified "gas flow rate/velocity", "figured" > "shown", "numerical concentration" > "number concentration", "volt-amphere > "current-voltage", "accepted.. " > "assumed to be..", "Follow technological parameters..."> "The following technological parameters..".

Reviewer comments and suggestions

Authors reply

1

Line 121. " 2.25 to 5.6 " please provide reference.

The Authors used fly ash dielectric parameters from Russian-language sources, such as [1]. English-language works, such as  [2], state the dielectric constant value of 2.1-3.06 for coal ash. Another work [3] investigates the dependence of the dielectric parameters of ash on the chemical composition and asserts the dielectric constant value for the studied lignite samples in the range of 2.9-3.7. in work [4], the measured dielectric constant values are presented in a range similar to that given in our work; the constant prediction method respecting the fly ash chemical composition is also presented, and corresponding calculations can confirm the values given by us. In our improvement manuscript, we do not discuss this issue to avoid littering the work, but we provide a relevant citations consecutively (Please see line 117).

2

Line 142. The secondary emission mechanisms due to back-corona discharge was recently studied by Krupa et al. Powder Technology 344 (2019) 475–486, indicating the dust eruption.

We believe the results of the referenced work are important and are therefore cited in our improved manuscript (Please see lines 137 and 138).

3

Table 2. Explain symbols W and A resulting from the CHNSO analysis.

Table 2 is corrected.

4

Line 238. Be specific what is the length of "45 mm"? Is it an inradius or circumradius, or side length? Show this dimension exactly in Figure 2. Line 348: Please indicate also the distance R at the scheme in Figure 2. Is it perpendicular to the hexagon side?

The design of the electrostatic precipitator involves honeycomb collecting electrodes with a hexagon side length of 45 mm, which corresponds to the radius of the circumscribed circle.

The distance between the electrodes R was measured in the direction perpendicular to the hexagon side and corresponded to the inscribed circle radius. This distance was used when the field in the honeycomb cell was approximated to a wire-to-cylinder electrode system. Katsov confirmed the inaccuracy of such an approximation as acceptable for engineering practice [5].

Figure 2 is updated.

5

Line 250. Was the supply voltage off during rapping of discharge electrodes to avoid breakdown/short circuit? Explain.

The electrodes were regenerated on a switched-off ESP after every single experiment. Rapping of the discharge and collecting electrodes was not required during measurements since the current and voltage values in the ESP were stable: obviously, dust collected on the electrode surface did not affect the electrical parameters. Please see lines 333-337.

The sparking and short circuits during the regeneration of discharge electrodes is a rather complex issue and requires special studies.

6

Line 349. The mobility of 2.1x10-4 m2/Vs is for normal conditions (Cobine, Gaseous Conductors). This value has to be recalculate to a temperature specific for electrostatic precipitator.

For precise physical science experiments, ion mobility should be surely evaluated respecting the gas temperature. However, we believe that using the mobility value for normal conditions introduces inaccuracy, which is acceptable for practical engineering and is much lower than the error introduced by approximations when calculating particle charges.

7

References. Missing journal or conference data, or webpage address in some references.

The references were improved

REVIEWER #2

The manuscript titled " Specifics of Electrostatic Precipitation of Fly Ash From Small-Scale Fossil Fuel Combustions" investigates the removal efficiency of the honeycomb electrostatic precipitator (ESP) applied to control the particulate matter (PM) emissions from the small-scale boiler with combustion lignite and hard coal. The overall methodology and manuscript are poorly written—many spelling and typo mistakes. The experiment description and results description are brief, whereas the introduction is quite long. I would recommend that the author should correct and submit it again.

Reviewer comments and suggestions

Authors reply

1

The spelling of the filter in Fig. 1 is needed to be corrected.

Figure 1 is corrected.

2

The explanation of the experimental setup should be increased.

Authors prefer concise texts and realise that

that the Introduction volume has been increased. Information on the electrostatic precipitation basics, the properties of fly ash, and related processes such as reverse corona or nucleation is approximately 800 words. Since our work is intended for a wide range of readers related to engineering, we consider this information necessary and provide it in a minimal volume, supplemented with references to more detailed information. In addition, we believe such an expanded Introduction to be reasonable since it avoids a new chapter and, therefore, reformulation.

We have tried to consistently describe the experimental setup measurement equipment and sampling technics, providing only the necessary information and introducing citations for details. We believe that this part of the manuscript contains all the information necessary to experiment replication and supports the discussion and argumentation of the correctness of the conclusions.

3

The results and discussion parts should be elaborated more, and the results should be compared with the latest research work; most references cited are quite old.

The result and discussion section is improved, please see lines 33-337 and 355-360. Referents have been replaced with newer ones wherever possible. However, some cited references are still actual and can be replaced, e.g. fundamental works of Deutsch [6] and White [7].

4

The equation numbers are not mentioned in the text.

The manuscript was improved. Please see lines 341,358-360 and 416.

5

Subscript mistakes in the text.

Subscripts were corrected all over the manuscript.