Method for resource utilization of clay vanadium-containing shale

Abstract

The invention discloses a method for resource utilization of clay vanadium-containing shale, and belongs to the field of solid waste resource utilization. Aiming at the situation that the clay vanadium-containing shale cannot be effectively utilized due to the fact that the vanadium grade is low and cannot meet the development and utilization requirements, so that resources are wasted, the vanadium grade in the clay vanadium-containing shale is improved through pre-enrichment, and the method mainly comprises the following process steps: (1) grading without grinding after crushing: crushing the clay vanadium-containing shale to be-(2-4 mm), and crushing the clay vanadium-containing shale to be-(2-4 mm); grinding is not needed, wet screening and grading are carried out with 25-45 [mu] m as the standard, oversize products and undersize products are obtained, and the undersize products are pre-enriched products I; (2) after-grinding three-section full-open-circuit short-process flotation is conducted on oversize products, the oversize products are ground to-74 microns and account for 50%-85%, then three-section full-open-circuit short-process flotation is conducted in the acid environment that the pH of ore pulp ranges from 3 to 4, and flotation concentrate is a pre-enriched product II; the collecting agent is compounded and assembled autonomously, and the novel combined collecting agent comprises the following components in percentage by mass: 50-75% of dodecyl guanidine hydrochloride and 25-50% of isooctyl alcohol. The combined inhibitor comprises the following components in percentage by mass: 30-50% of water glass and 50-70% of sodium fluosilicate.

Description

Technical Field

[0001] The invention relates to a method for resource utilization of clayey vanadium-containing shale, and belongs to the field of solid waste resource utilization. Background Art

[0002] Clayey vanadium-bearing shale is a low-grade vanadium ore and a mineral resource unique to China. It can be used as a potential raw material for vanadium extraction. In today's vanadium market, it is generally believed that vanadium grade (measured in V2O5, the same below) is greater than 1.5%, which is economically valuable for extraction, that is, resource utilization value. However, the grade of most clayey vanadium-bearing shale is significantly less than 1.5%, which has led to clayey vanadium-bearing shale being regarded as solid waste and discarded for a long time, and has not been developed and utilized, resulting in serious waste of resources. Therefore, it is undoubtedly of great significance if the vanadium grade of clayey vanadium-bearing shale can be improved by a simple and environmentally friendly pre-enrichment method before vanadium extraction to meet the requirements of resource utilization.

[0003] In view of the important role of pre-enrichment in the resource utilization of clayey vanadium-bearing shale (i.e., economic vanadium extraction), metallurgical workers have conducted research on this and produced a large number of process methods. However, these process methods are basically only in the laboratory stage and are difficult to promote and apply. In addition, there are the following problems: (1) The existing pre-enrichment process methods have poor applicability and are basically not applicable to low-grade clayey vanadium-bearing shale, and the process is relatively complicated; (2) The existing pre-enrichment process methods have a relatively limited enrichment degree: the degree of improvement in vanadium grade is basically less than one percentage point; in some cases, for specific vanadium-bearing shale in a specific area, the pre-enrichment degree can exceed one hundred by using complex process methods. (3) Conventional and traditional flotation reagents are difficult to meet the requirements of pre-enrichment of mineral processing: Flotation is more promising. Compared with gravity separation, it can generally obtain pre-enrichment products with higher grades. The existing flotation pre-enrichment reagents are basically transplanted from conventional and traditional flotation reagents. However, due to the unique properties of vanadium-containing shale, its mineral composition is much more complex than that of common flotation ore. Therefore, conventional and traditional flotation reagents are difficult to meet the requirements of pre-enrichment of mineral processing, and often there will be problems such as difficulty in flotation of vanadium-containing minerals, large reagent consumption and poor selectivity.

[0004] Therefore, in order to realize the development and utilization of clayey vanadium-containing shale as a solid waste resource, it is now urgent to develop a new method for the resource utilization of clayey vanadium-containing shale, that is, a new method for pre-enrichment of clayey vanadium-containing shale, so as to improve the vanadium grade of clayey vanadium-containing shale and meet the requirements of economical vanadium extraction. Summary of the invention

[0005] In order to realize the resource utilization of clayey vanadium-containing shale and solve the problems existing in the existing pre-enrichment process, the present invention provides a method for resource utilization of clayey vanadium-containing shale, which effectively improves the vanadium grade of clayey vanadium-containing shale through pre-enrichment treatment, so that it can meet the resource utilization requirements well, and is conducive to subsequent low-cost, low-consumption, clean and environmentally friendly vanadium extraction. The specific method is as follows:

[0006] (1) Classification without grinding after crushing: The clayey vanadium-containing shale is crushed, and then water is added to the slurry for wet screening and classification without grinding to obtain the oversize and undersize materials, and the undersize materials are the pre-enrichment product I;

[0007] (2) grinding the oversize material and subjecting it to three-stage full-open circuit short-process flotation: grinding the oversize material obtained in step (1) to obtain finely ground ore pulp, adjusting the pH value of the ore pulp, and subjecting it to three-stage full-open circuit short-process flotation in an acidic environment. The concentrates from the three-stage full-open circuit short-process flotation are combined as pre-enriched product II; and in the flotation process, a combined collector prepared by combining dodecylguanidine hydrochloride and isooctyl alcohol and a combined inhibitor prepared by combining water glass and sodium fluorosilicate are used.

[0008] Preferably, the vanadium grade of the pre-enriched product I obtained in step (1) and the pre-enriched product II obtained in step (2) reaches or exceeds the requirement for resource utilization and can be directly used for vanadium extraction.

[0009] Preferably, in step (1), the clayey vanadium-containing shale is crushed to -(2-4 mm).

[0010] Preferably, in step (1), a sieve of 325 to 500 mesh is used for wet screening and grading, and the obtained undersize is of -(25 to 45 μm) particle size; and the oversize is of +(25 to 45 μm) particle size.

[0011] Preferably, in step (2), the oversize is ground to -74 μm with an occupancy rate of 50 to 85%; the acidic environment refers to a slurry pH value of 3 to 4.

[0012] Preferably, the combined collector in step (2) is composed of 50-75% dodecylguanidine hydrochloride and 25-50% isooctyl alcohol, and the total mass percentage of dodecylguanidine hydrochloride and isooctyl alcohol is 100%.

[0013] Preferably, in step (2), the combined inhibitor is composed of 30-50% water glass and 50-70% sodium fluorosilicate, and the total mass percentage of water glass and sodium fluorosilicate is 100%.

[0014] Preferably, the three-stage open circuit short-process flotation in step (2) includes stage I open circuit flotation, stage II open circuit flotation and stage III open circuit flotation; in stage I open circuit flotation, the amount of combined collector is 200-400 g / t, and the amount of combined depressant is 600-1000 g / t; in stage II open circuit flotation, the amount of combined collector is 100-200 g / t, and the amount of combined depressant is 300-500 g / t; in stage III open circuit flotation, the amount of combined collector is 50-100 g / t, and the amount of combined depressant is 150-250 g / t.

[0015] Preferably, in step (2), dilute H2SO4 is used to adjust the pH of the slurry.

[0016] Preferably, the clayey vanadium-containing shale of the present invention has a yellow to brown appearance and is flaky, the flaky interlayer is clay, the SiO2 content is not less than 75%, the vanadium grade (measured in V2O5, the same below) is 0.3-0.8%, and it is a low-grade clayey vanadium-containing shale.

[0017] After adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0018] (1) Clayey vanadium-bearing shale has its own particularity. Illite, vanadium mica and kaolinite coexist in cryptocrystalline interlayers. They are easily muddied during the crushing process. Even if they are not ground after crushing, a large number of fine particles will be produced. The target component vanadium is partially distributed in the fine particle size (fine particles). Generally speaking, the finer the particle size, the higher the vanadium content (i.e., the enrichment degree) in it. In other words, through simple and environmentally friendly wet screening and grading, the purpose of partial vanadium classification pre-enrichment can be fully achieved (the undersize is the fine particle size, which is enriched and enters the subsequent vanadium extraction process; in order to improve the recovery rate of vanadium, the oversize is the coarse particle size, which is treated separately to further enrich vanadium).

[0019] At the same time, through simple and environmentally friendly wet screening and grading, fine particles in clayey vanadium-containing shale have been recovered, which can avoid the adverse effect of clayey vanadium-containing shale on the next flotation pre-enrichment due to easy mudification (a large number of fine clay particles, if entering the slurry, will deteriorate the flotation process and make the flotation process difficult to control). The existing pre-enrichment process methods basically grind all the raw ores, while the present invention recovers the fine particle size (screen undersize) in advance by not grinding and grading after crushing, and only grinds the coarse particle size (screen oversize), which can increase the effective processing capacity of the mill, reduce the energy consumption of the mill, and increase the processing capacity.

[0020] (2) Flotation is a mineral processing method that is currently widely used to enrich vanadium-containing minerals. However, the existing flotation pre-enrichment process generally requires decarbonization and desludging pretreatment, which is generally a "roasting decarbonization-desludging-closed-circuit flotation" process, which has the disadvantages of long process, complex process, and large amount of reagents. The present invention adopts "full open-circuit short-circuit flotation after grinding the oversize material". The simple three-stage open-circuit flotation can meet the requirements, which not only avoids the adverse effects of deteriorating the flotation environment, reducing the quality of the concentrate, and affecting the enrichment degree caused by the return of the middling ore, but also has a simple process and is easy to operate and implement.

[0021] In vanadium-containing shale, useful minerals are mainly vanadium-containing aluminosilicates (represented by mica, garnet, etc.), and gangue minerals are mainly quartz. Therefore, flotation pre-enrichment of vanadium-containing shale is essentially the separation of aluminosilicates and quartz. There are some studies on the flotation separation of aluminosilicates and quartz, but these studies only examine the influence of the main factors, and there are still a series of problems such as large reagent consumption, poor selectivity, and unsatisfactory pre-enrichment effect. In the present invention, the collector and the inhibitor are independently compounded and assembled, which has the advantages of strong pertinence, high selectivity, small reagent consumption, and low reagent cost. It can effectively realize the separation of aluminosilicates and quartz (i.e., pre-enrichment of vanadium), and simplify the flotation process. The purpose of pre-enrichment can be achieved by three-stage open-circuit flotation.

[0022] (3) The flotation pre-enrichment of vanadium-containing shale is essentially the separation of aluminosilicate and quartz; since quartz has similar physical properties, chemical composition and surface charge to silicate minerals, it is very difficult to separate the two by flotation. Most existing technologies use alkaline earth metal ions as activators and alkyl sulfonates as collectors under highly alkaline environmental conditions to preferentially capture quartz, thereby achieving the separation of quartz and aluminosilicate minerals and achieving the purpose of pre-enrichment. Although the impact of strong acid on the environment can be avoided under alkaline conditions, considering the subsequent vanadium extraction process (generally acid leaching vanadium extraction), flotation in an acidic environment can save the amount of sulfuric acid used in the subsequent acid leaching vanadium extraction to the greatest extent; in addition, quartz is a typical oxide mineral, and its flotation behavior has been widely studied. The results show that cationic collectors give quartz a good recovery rate at a higher pH value (alkaline environment), which obviously cannot achieve the purpose of effective separation; at the same time, the recovery rates of some silicate minerals, such as kaolinite, illite and garnet, increase with the decrease of pH value, and the acidic environment is more conducive to the flotation of aluminum silicate minerals. Therefore, the present invention performs flotation pre-enrichment in an acidic environment with a pulp pH of 3 to 4, which is obviously more advantageous.

[0023] (4) Collectors play the most important role in achieving flotation pre-enrichment. Dodecylamine (DDA) is the most commonly used cationic collector for silicate mineral flotation. It is mainly adsorbed on the mineral surface by electrostatic attraction, making the target mineral surface hydrophobic, easy to adhere to bubbles, and enhancing floatability. In the present invention, dodecylguanidine hydrochloride (DDGH) is selected as the collector because it is more + H3 group (in DDA + cation), —NHC(NH)N + H3 group (in DDG + cations) can be better adsorbed on silicate minerals through hydrogen bonding.

[0024] In addition, a single collector often has the disadvantages of high consumption, poor selectivity, and poor separation effect. By controlling the type and compounding ratio of the collector to exert synergistic effects, a better flotation pre-enrichment effect can be obtained. In silicate mineral flotation, alcohol can be used as an auxiliary collector, and adding non-ionic collectors (alcohols) to the main collector can improve the selectivity of the collector, reduce the dosage of the main collector and mechanical entrainment, and improve foam stability. In view of this, the collectors are independently compounded and assembled in the present invention, and the mass composition ratio of the new combined collector DDGH-2-EH is: 50-75% dodecylguanidine hydrochloride (DDGH), 25-50% isooctyl alcohol (2-EH).

[0025] (5) Since aluminosilicate and quartz have similar floatability, selective inhibition of quartz is particularly important. Commonly used agents for inhibiting quartz are water glass, sodium fluorosilicate, etc., but the selectivity of a single inhibitor is often poor and the consumption is very high. Therefore, the present invention selects to use water glass and sodium fluorosilicate in combination, and the mass component ratio of the combined inhibitor is: 30-50% water glass, 50-70% sodium fluorosilicate, which can play a positive synergistic role and show a better selective inhibition effect under low consumption conditions, thereby facilitating the separation of aluminosilicate and quartz.

[0026] Combining the above aspects, a method for resource utilization of clayey vanadium-containing shale can effectively improve the vanadium grade through pre-enrichment treatment to meet the requirements of resource utilization, and is conducive to subsequent low-cost, low-consumption, clean and environmentally friendly vanadium extraction; at the same time, the new method of the present invention has a simple process, low consumption, environmental protection, and easy operation and implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following embodiments are merely simple examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0029] Example 1

[0030] The clayey vanadium-containing shale used in this embodiment is yellow in appearance and flaky. The flaky interlayer is clay, and the SiO2 content is 80.34%. The vanadium grade is only 0.72%, which is a low-grade clayey vanadium-containing shale.

[0031] The combined collector used in this example is composed of 50% dodecylguanidine hydrochloride and 50% isooctyl alcohol; the combined inhibitor is composed of 50% water glass and 50% sodium fluorosilicate.

[0032] A method for resource utilization of clayey vanadium-containing shale, the specific process of pre-enrichment process is as follows: Figure 1 The specific steps are as follows:

[0033] (1) Classification without grinding after crushing: The clayey vanadium-containing shale is crushed to -3 mm, and then, without grinding, water is added to make a slurry and wet screening and classification is performed with 400 mesh (i.e., 38 μm) as the standard to obtain the oversize and undersize. The undersize is the -38 μm particle size and is the pre-enrichment product I.

[0034] (2) Fully open circuit short process flotation after grinding the oversize: The oversize obtained in step (1), i.e., the +38 μm particle size, is ground to -74 μm with an occupancy rate of 65%, and the pH value of the slurry is adjusted to 3 with dilute H2SO4, followed by three-stage open circuit short process flotation. In stage I open circuit flotation, the amount of combined depressant is 1000 g / t, and the amount of combined collector is 200 g / t; in stage II open circuit flotation, the amount of combined depressant is 500 g / t, and the amount of combined collector is 100 g / t; in stage III open circuit flotation, the amount of combined depressant is 250 g / t, and the amount of combined collector is 50 g / t; the concentrates from the three stages of open circuit flotation are combined as pre-enrichment product II.

[0035] The vanadium grade of the pre-enriched product obtained in this embodiment is 2.31% and the recovery rate is 89.77%, which effectively realizes the pre-enrichment of vanadium and well meets the requirements of resource utilization of clayey vanadium-containing shale. In addition, the process is simple, low-consumption, environmentally friendly, and easy to operate.

[0036] Example 2

[0037] The clayey vanadium-containing shale used in this embodiment is yellow in appearance and flaky. The flaky interlayer is clay, with a SiO2 content of 82.79% and a vanadium grade of only 0.68%, which is a low-grade clayey vanadium-containing shale.

[0038] The combined collector used in this example is composed of 60% dodecylguanidine hydrochloride and 40% isooctyl alcohol; the combined inhibitor is composed of 40% water glass and 60% sodium fluorosilicate.

[0039] A method for resource utilization of clayey vanadium-containing shale, the specific process of pre-enrichment process is as follows: Figure 1 The specific steps are as follows:

[0040] (1) Classification without grinding after crushing: The clayey vanadium-containing shale is crushed to -3 mm, and then, without grinding, water is added to make a slurry and wet screening and classification is performed with 400 mesh (i.e., 38 μm) as the standard to obtain the oversize and undersize. The undersize is the -38 μm particle size and is the pre-enrichment product I.

[0041] (2) Fully open circuit short process flotation after grinding the oversize: The oversize obtained in step (1), i.e., the +38 μm particle size, is ground to -74 μm with an occupancy rate of 75%, and the pH value of the slurry is adjusted to 3.5 with dilute H2SO4, followed by three-stage open circuit short process flotation. In stage I open circuit flotation, the amount of combined depressant is 800 g / t, and the amount of combined collector is 300 g / t; in stage II open circuit flotation, the amount of combined depressant is 400 g / t, and the amount of combined collector is 150 g / t; in stage III open circuit flotation, the amount of combined depressant is 200 g / t, and the amount of combined collector is 75 g / t; the concentrates of the three stages of open circuit flotation are combined as pre-enrichment product II.

[0042] The vanadium grade of the pre-enriched product obtained in this embodiment is 2.27% and the recovery rate is 88.45%, which effectively realizes the pre-enrichment of vanadium and well meets the requirements of resource utilization of clayey vanadium-containing shale. In addition, the process is simple, low-consumption, environmentally friendly, and easy to operate.

[0043] Example 3

[0044] The clayey vanadium-containing shale used in this embodiment is yellow in appearance and flaky. The flaky interlayer is clay, with a SiO2 content of 85.11% and a vanadium grade of only 0.63%, which is a low-grade clayey vanadium-containing shale.

[0045] The combined collector used in this example is composed of 75% dodecylguanidine hydrochloride and 25% isooctyl alcohol; the combined inhibitor is composed of 30% water glass and 70% sodium fluorosilicate.

[0046] A method for resource utilization of clayey vanadium-containing shale, the specific process of pre-enrichment process is as follows: Figure 1 The specific steps are as follows:

[0047] (1) Classification without grinding after crushing: The clayey vanadium-containing shale is crushed to -2 mm, and then, without grinding, water is added to make a slurry and wet screening and classification is performed with 500 mesh (i.e., 25 μm) as the standard to obtain the oversize and undersize. The undersize is the -25 μm particle size and is the pre-enrichment product I.

[0048] (2) Fully open circuit short process flotation after grinding the oversize: The oversize obtained in step (1), i.e., the +45 μm particle size, is ground to -74 μm with an occupancy rate of 85%, and the pH value of the slurry is adjusted to 4 with dilute H2SO4, followed by three-stage open circuit short process flotation. In stage I open circuit flotation, the amount of combined depressant is 600 g / t, and the amount of combined collector is 400 g / t; in stage II open circuit flotation, the amount of combined depressant is 300 g / t, and the amount of combined collector is 200 g / t; in stage III open circuit flotation, the amount of combined depressant is 150 g / t, and the amount of combined collector is 100 g / t; the concentrates from the three stages of open circuit flotation are combined as pre-enrichment product II.

[0049] The vanadium grade of the pre-enriched product obtained in this embodiment is 2.25% and the recovery rate is 88.36%, which effectively realizes the pre-enrichment of vanadium and well meets the requirements of resource utilization of clayey vanadium-containing shale. In addition, the process is simple, low-consumption, environmentally friendly, and easy to operate.

[0050] Comparative Example 1

[0051] As a comparison, the difference from Example 3 is that only dodecylamine is used as the collector, the clayey vanadium-containing shale and the combined inhibitor used are the same as those in Example 3, the specific process flow is the same as that in Example 3, and the specific process flow of the pre-enrichment process is as follows: Figure 1 The specific steps are as follows:

[0052] (1) Classification without grinding after crushing: The clayey vanadium-containing shale is crushed to -2 mm, and then, without grinding, water is added to make a slurry and wet screening and classification is performed with 500 mesh (i.e., 25 μm) as the standard to obtain the oversize and undersize. The undersize is the -25 μm particle size and is the pre-enrichment product I.

[0053] (2) Fully open circuit short process flotation after grinding the oversize: The oversize obtained in step (1), i.e., the +45 μm particle size, is ground to -74 μm with an occupancy rate of 85%, and the pH value of the slurry is adjusted to 4 with dilute H2SO4, followed by three-stage open circuit short process flotation. In stage I open circuit flotation, the amount of combined depressant is 600 g / t, and the amount of collector dodecylamine is 400 g / t; in stage II open circuit flotation, the amount of combined depressant is 300 g / t, and the amount of collector dodecylamine is 200 g / t; in stage III open circuit flotation, the amount of combined depressant is 150 g / t, and the amount of collector dodecylamine is 100 g / t; the concentrates of the three stages of open circuit flotation are combined as pre-enrichment product II.

[0054] The vanadium grade of the pre-enriched product obtained in this embodiment is only 1.37%, and the recovery rate is only 75.42%. The effect is not as good as that of Example 3. The reason is that:

[0055] Collectors play the most important role in achieving flotation pre-enrichment. Dodecylamine (DDA) is the most commonly used cationic collector for silicate mineral flotation. It is mainly adsorbed on the mineral surface by electrostatic attraction, making the target mineral surface hydrophobic, easy to adhere to bubbles, and enhancing floatability. The present invention selects dodecylguanidine hydrochloride (DDGH) as the collector because compared with -N + H3 group (in DDA + cation), —NHC(NH)N + H3 group (in DDG + cations) can be better adsorbed on silicate minerals through hydrogen bonding.

[0056] In addition, a single collector often has the disadvantages of high consumption, poor selectivity, and poor separation effect. By controlling the type and proportion of the collector and making it work synergistically, a better flotation pre-enrichment effect can be obtained. In silicate mineral flotation, alcohol can be used as an auxiliary collector, and adding non-ionic collectors (alcohols) to the main collector can improve the selectivity of the collector, reduce the dosage of the main collector and mechanical entrainment, and improve the stability of the foam.

Claims

1. A method for resource utilization of clayey vanadium-containing shale, characterized by: The specific steps are as follows: (1) Classification without grinding after crushing: The clayey vanadium-containing shale is crushed, and then water is added to the slurry for wet screening and classification without grinding to obtain the oversize and undersize materials, and the undersize materials are the pre-enrichment product I; (2) grinding the oversize and then flotating it in three stages of full open circuit short process: grinding the oversize obtained in step (1) to obtain finely ground slurry, adjusting the pH value of the slurry, and flotating it in three stages of full open circuit short process in an acidic environment. The concentrates from the three stages of full open circuit short process flotation are combined as pre-enriched product II; during the flotation process, a combined collector prepared by combining dodecylguanidine hydrochloride and isooctyl alcohol and a combined inhibitor prepared by combining water glass and sodium fluorosilicate are used.

2. The method for resource utilization of clayey vanadium-containing shale according to claim 1, characterized in that: The pre-enriched product I obtained in step (1) and the pre-enriched product II obtained in step (2) can be directly used for subsequent vanadium extraction.

3. The method for resource utilization of clayey vanadium-containing shale according to claim 1, characterized in that: In step (1), the clayey vanadium-containing shale is crushed to – (2-4 mm).

4. The method for resource utilization of clayey vanadium-containing shale according to claim 1, characterized in that: In step (1), a 325-500 mesh screen is used for wet screening and grading, and the obtained undersize is a -(25-45 μm) particle size, and the oversize is a +(25-45 μm) particle size.

5. The method for resource utilization of clayey vanadium-containing shale according to claim 1, characterized in that: In step (2), the ore is ground to -74 μm with an occupancy rate of 50 to 85%; the acidic environment refers to a pH value of the ore pulp of 3 to 4.

6. The method for resource utilization of clayey vanadium-containing shale according to claim 1, characterized in that: In step (2), the combined collector is composed of 50-75% dodecylguanidine hydrochloride and 25-50% isooctyl alcohol, and the total mass percentage of dodecylguanidine hydrochloride and isooctyl alcohol is 100%.

7. The method for resource utilization of clayey vanadium-containing shale according to claim 1, characterized in that: In step (2), the combined inhibitor is composed of 30-50% water glass and 50-70% sodium fluorosilicate, and the total mass percentage of water glass and sodium fluorosilicate is 100%.

8. The method for resource utilization of clayey vanadium-containing shale according to claim 1, characterized in that: The three-stage full-open circuit short-circuit flotation in step (2) includes stage I open circuit flotation, stage II open circuit flotation and stage III open circuit flotation; in stage I open circuit flotation, the dosage of the combined collector is 200-400 g / t, and the dosage of the combined depressant is 600-1000 g / t; in stage II open circuit flotation, the dosage of the combined collector is 100-200 g / t, and the dosage of the combined depressant is 300-500 g / t; in stage III open circuit flotation, the dosage of the combined collector is 50-100 g / t, and the dosage of the combined depressant is 150-250 g / t.

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