Research on the Selective Grinding of Zn and Sn in Cassiterite Polymetallic Sulfide Ore

Round 1

Reviewer 1 Report

The order and degree of mineral dissociation affects the beneficiation process and index. This paper investigates the process of selective grinding in a simple and innovative approach. A minor amount of revision is also required before the paper for publication. 

1. A detailed description of the grinding process would be beneficial to the reader's understanding.
2. It is suggested that information on zinc minerals in ore be checked.
3. It is suggested to check the content of lines 69-73, as if j is not mentioned in the formula.

Author Response

Question 1:

A detailed description of the grinding process would be beneficial to the reader's understanding.

Response 1:

Thank you very much for your suggestion. According to your suggestion, we have made a revision in the revised manuscript. As follows:

“Grinding is the process of reducing the particle size of ore and providing qualified selected materials for subsequent separation operations with the help of the impact and grinding of medium on ore in grinding equipment. Its main task is to maximize the dissociation of useful minerals and gangue minerals in the ore, so as to provide materials whose particle size meets the requirements of the next beneficiation process.”

Question 2:

It is suggested that information on zinc minerals in ore be checked.

Response 2:

Special thanks to you for your good comments. According to your suggestion, we have made a revision in the revised manuscript. As follows:

The chemical composition and distribution rate of Zn and Sn metals in each particle size are shown in Table 1 and 2 respectively.

Table 1 Chemical components of the sample

Component	SiO2	CaCO3	Fe2O3	SO3	Al2O3	Zn	K2O
Content/%	49.9	22.3	10.1	7.7	3.9	2.0	0.9
Component	MgO	Sn	As	P2O5	Pb	Sb	Other
Content/%	0.6	0.6	0.6	0.4	0.4	0.2	0.36

Table 2 Grade and metal distribution of Zn and Sn in the sample

Particle size/mm	Zn			Sn
	Grade/%	Metal distribution/%	Cumulative metal distribution on sieve/%	Grade/%	Metal distribution/%	Cumulative metal distribution on sieve/%
-3.0+0.425	1.33	40.77	40.77	0.39	53.78	53.78
-0.425+0.150	3.24	21.32	62.09	0.60	17.78	71.56
-0.150+0.075	4.78	12.24	74.33	0.92	10.67	82.23
-0.075+0.038	4.66	8.39	82.72	0.68	5.33	87.56
-0.038	2.44	17.28	100.00	0.39	12.44	100.00

Question 3:

It is suggested to check the content of lines 69-73, as if j is not mentioned in the formula.

Response 3:

Thank you very much for your suggestion. According to your suggestion, we have made a revision in the revised manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

It is impossible to properly evaluate this paper or to understand the results until the methods used to generate the various parameters outlined in Section 2.2 are more clearly explained. The authors should at least show one or two sets of raw data from the milling experiments are converted into the various parameters shown in equations 1 and 2. 

Comments for author File: Comments.pdf

Author Response

Respond to reviewer :

Main question:

It is impossible to properly evaluate this paper or to understand the results until the methods used to generate the various parameters outlined in Section 2.2 are more clearly explained. The authors should at least show one or two sets of raw data from the milling experiments are converted into the various parameters shown in equations 1 and 2.

Response:

Thank you very much for your suggestion. According to your suggestion, we have made changes in the revised manuscript. As follows:

Table 3 The analysis results of grinding product when grinding time is 2min

i	Particle size/mm	/g	/%	/%	/%	/%
1	-3.00+0.425	207.6	42.28	1.03	0.39	1.03
2	-0.425+0.150	105.56	21.50	2.43	0.56	1.50
3	-0.150+0.075	41.41	8.43	3.99	0.74	1.79
4	-0.075+0.038	27.63	5.63	3.52	0.41	1.92
5	-0.038	108.82	22.16	2.53	0.37	2.05
—	Total	491.02	100.00	2.05	0.45	——
i	Particle size/mm	/%	/g	/g	/g	/g
1	-3.00+0.425	0.39	2.14	0.81	2.14	0.81
2	-0.425+0.150	0.45	2.57	0.59	4.71	1.40
3	-0.150+0.075	0.48	1.65	0.31	6.36	1.71
4	-0.075+0.038	0.48	0.97	0.11	7.33	1.82
5	-0.038	0.45	2.75	0.40	10.08	2.22
—	Total	——	10.08	2.22	——	——

General question:

Question 1:

Can the authors validate the comment that cassiterite is usually on top of the bed of particles in the ball mill.

Response 1:

Thank you very much for your suggestion. According to your suggestion, we have made changes in the revised manuscript. As follows:

“When cassiterite polymetallic sulfide ore being grinded in the ball mill, the contradiction between over grinding of cassiterite and under grinding of sulfide ore is inevitable due to their mechanical property differences.”

Question 2:

This is quite confusing. For example in the equation 1 the 2nd term is “represents the changes in the cumulative grade of particles 67 above size i in raw mineral A in %”. Changes must be relative to something!!

To what is the change compared? Similarly line 71 refers to “as the yield of particle size j of the raw ore in %” What is the meaning of the word “yield” in this context? These need to be much more carefully defined.

Response 2:

Thank you very much for your suggestion. According to your suggestion, we have made changes in the revised manuscript.

Assuming that the whole material is composed of four mineral components: “A”, “B”, “C” and “D”, we take “A” as an example to discuss its selective grinding. As shown in Figure 1, it is assumed that “a” is the original state of material composition, and “b”, “c” and “d” are three different types of states of materials (converted to the original particle size) that are ground after a period of grinding time. State “b” is that mineral “A” is broken more and the grade decreases; “c” state is equal probability crushing and the grade remains unchanged; “d” state is that mineral “A” is less broken and the grade increases. It can be seen from Figure 1 that as long as the content of mineral “A” in the remaining material on the screen is known, we can judge what type of crushing has occurred to mineral “A”.

Therefore, for a material, a screening size is used to divide the material into two. As long as the content change of each mineral in the remaining part is investigated, we can know whether a mineral has been preferentially broken, that is, whether selective grinding has occurred. In fact, the first mock exam is equivalent to the change of accumulated grade on a sieve particle size sieve before and after grinding. Therefore, the cumulative metal grade change value on a mineral sieve can be designed as an evaluation index. The cumulative metal grade change on the sieve can be characterized by equation 1.

 

Fig.1 The grinding of mineral A

The content of line 71 has been modified. In addition, the yield refers to the percentage of the mass of a certain particle size in the grinding product to the mass of raw ore.

Question 3:

If the 1st term in eqn. 1 is negative then the 3rd term is greater than the second term. Can the authors be much more specific and clearer as to what conditions/situations would cause this.

Response 3:

Thank you very much for your suggestion. According to your suggestion, we have made changes in the revised manuscript.

Question 4:

Similarly what does the condition, “the cumulative grade of particle sizes above i remains unchanged” imply?

Response 4:

Thank you very much for your suggestion. According to your suggestion, we have made changes in the revised manuscript. As follows:

“In contrast, when the cumulative grade is greater than zero, the cumulative grade of particle sizes above i gets greater. When the cumulative grade is greater than zero, the cumulative grade of particle sizes above i remains unchange and mineral A is not preferentially broken.”

Question 5:

What is the meaning of “cumulative quantity of metal”?

Response 5:

Thank you very much for your suggestion. “Cumulative quantity of metal” refers to the cumulative metal mass of a mineral with particle size above or below a certain particle size.

Question 6:

The statement: “In comparison, the smaller A i rm, is to B i rm, the higher the grinding priority of mineral A will be to that of mineral B. In other words, the selectivity of the grinding becomes more pronounced. On the other hand, when A i rm, is greater than B i rm, vice versa” is not at all clear!!.

Response 6:

Thank you very much for your suggestion. Assuming that there are two mineral components “A” and “B” in the material to be ground, assuming that the mass of “A” and “B” before grinding is “ma” and “mb” respectively, and the probability of crushing is “pA” and “pB” respectively, the amount of “A” and “B” minerals crushed is “pA·ma” and “pB·mb” respectively, then the residual amount of “A” and “B” minerals after crushing are “ma－pA·ma” and “mb－pB·mb” respectively. The probability of A and B being broken, pA and pB, is actually the negative value of the relative change value of the metal amount of A and B before and after crushing. Therefore,  and  can use the relative change value of the accumulated metal amount on the sieve of these two minerals as the index to evaluate the preferential and selective grinding of the two mineral components.

Question 7:

What precisely is meant by “grinding concentration”? The phase “fill rate” is wrong. Rate is a kinetic term i.e. something/time!.

Response 7:

Thank you very much for your suggestion. Grinding concentration refers to the percentage of the weight of ore (dry weight) in the whole pulp (the sum of ore and water mass) in the grinding machine. In addition, the fill rate has been revised in the revised manuscript, and the correct one should be "filling ratio".

Question 8:

It is not possible to understand how the values shown in Table 1 are obtained until the meaning of all the above is explained much more clearly. It may be useful for the authors to present a detailed set of calculations using the raw data from the milling experiments to show how at least some of the value in this Table were obtained even if this is done for the 1st row in the Table (-3+- .425mm).

Response 8:

Thank you very much for your suggestion. According to your suggestion, we have made changes in the revised manuscript. In order to understand the data conversion process, we listed the raw data of grinding products when the grinding time was 2min, as shown in Table 3.

Question 9:

Again the authors should show how the values for the changes were obtained.

Response 9:

Thank you very much for your suggestion. According to your suggestion, we have made changes in the revised manuscript. In order to understand the data conversion process, we listed the raw data of grinding products when the grinding time was 2min, as shown in Table 3. In addition, in order to understand the derivation process of equation 1, we list its most original ideas and schematic diagram, as shown in Figure 1.

Question 10:

It is not possible to critically review this section given the fact that the method used to generate the abscissa data is not at all clear.

Response 10:

Special thanks to you for your good comments. According to your suggestion, we have made a revision in the revised manuscript.

Question 11:

How is it possible for Sn particles to be crushed into coarser particles–is there some aggregation phenomenon occurring?

Response 11:

Thank you very much for your suggestion. This means that Sn is more likely to be contained in coarse-grained grinding products in the grinding process of Sn containing minerals, rather than aggregation.

Author Response File: Author Response.pdf

Reviewer 3 Report

The paper “Research of the Selective Grinding of Zn and Sn in Cassiterite Polymetallic Sulfide Ore”, by Jinlin Yang et al., investigates the behaviors in the grinding process of two different minerals, due to their unique mechanical properties.

In my opinion, the paper presents enough quality to be published in “Minerals”.

The paper is very interesting, with practical conduction and conclusions.

However, I suggest some minor modifications:

In topic 2 (Materials and Methods), please describe the mill used in the paper.

Line 165. Correct in all text: -3 +0.425 mm or -3+0.425 mm (choose one and use always the same), and not -3 + 0.425 mm

The quality of the figures is good and easy to understand.

The references are old and most of them are in Chinese. You can find several new publications in the area. Please, add some new publications.

In general, the paper is interesting and presents the quality to be published.

I can not opine about the English.

Author Response

Respond to reviewer:

Question 1:

In topic 2 (Materials and Methods), please describe the mill used in the paper.

Response 1:

Thank you very much for your suggestion. According to your suggestion, we have made a revision in the revised manuscript. As follows: “Grinding experiments were carried out using a ball mill (XMQ-Ф240×90). ”

Question 2:

Line 165. Correct in all text: -3 +0.425 mm or -3+0.425 mm (choose one and use always the same), and not -3 + 0.425 mm.

Response 2:

Thank you very much for your suggestion. According to your suggestion, we have made a revision in the revised manuscript.

Question 3:

The references are old and most of them are in Chinese. You can find several new publications in the area. Please, add some new publications.

Response 3:

Special thanks to you for your good comments. According to your suggestion, we have made a revision in the revised manuscript.

Author Response File: Author Response.pdf