A cascade comprehensive recovery process for low-grade polymetallic sulfide ore

Abstract

The present invention belongs to the field of mineral processing technology, and specifically relates to a cascade comprehensive recovery process for low-grade polymetallic sulfide ores. A new cascade separation process of "copper priority flotation-sulfur-cobalt mixed flotation-sulfur-cobalt flotation separation" is adopted, and a sulfur combination inhibitor (composed of tannin, citric acid and ammonium silicate in a mass ratio of 1:1:1 to 2:1:1), a collector (ethylthiocarbamate), a foaming agent (propylene glycol ethyl ether), a combination collector (amyl xanthate and butyl ammonium black medicine in a mass ratio of 5:1 to 2:1), and a sulfur-cobalt separation inhibitor (sodium bisulfite and disodium ethylenediaminetetraacetic acid in a mass ratio of 2:1 to 4:1) is used to obtain a stable flotation effect under weakly alkaline conditions of the ore pulp, thereby realizing the green and low-carbon cascade comprehensive recovery of low-grade copper polymetallic sulfide ores, especially the effective recovery of associated cobalt minerals in the ore.

Description

Technical Field

[0001] The invention belongs to the technical field of ore dressing, and in particular relates to a cascade comprehensive recovery process of low-grade polymetallic sulfide ores with associated copper and cobalt. Background Art

[0002] Copper and cobalt are important strategic mineral resources in my country. With the deepening of mining and the reduction of easily selectable ores, the characteristics of copper, cobalt and sulfur ore resources such as "poor, fine, mixed and accompanied" have become increasingly prominent, and the mineral symbiosis and mosaic relationship have become more complex and changeable, making comprehensive recovery difficult and costly. The number and scale of newly discovered major copper mines are showing a sharp decline, and the reserves of medium- and long-term copper mine projects are worrying. The decline in grade has become a long-term trend, resulting in rising copper mine costs and pressure on production. The gap between supply and demand of copper mines in my country continues to widen, and the degree of external dependence has repeatedly reached new highs.

[0003] The separation of polymetallic sulfide ores is a typical polymetallic sulfide ore beneficiation problem. By conducting high-efficiency flotation technology research on copper-sulfur ores, selective separation of copper, cobalt and sulfur can be achieved, and high-quality copper, cobalt and sulfur concentrates can be produced, thereby increasing economic value. This is the only way to achieve sustainable development of domestic copper mines and one of the effective ways to break through the bottleneck of copper smelting technology from the source. Therefore, it is of great significance to increase the efficient and comprehensive recovery and utilization of key valuable elements such as copper, cobalt and sulfur associated with existing (extremely) low-grade copper polymetallic ores.

[0004] Copper-containing polymetallic ores mainly include copper-lead-zinc-sulfur ores, copper-molybdenum ores, copper-sulfur ores, copper-bismuth ores, copper-nickel ores, etc. These ores are often difficult to separate by flotation due to their complex mineral composition, multiple metal minerals to be comprehensively recovered, close symbiotic relationships between minerals, and small differences in floatability between metal minerals. In recent years, mineral processing research has mainly focused on the development and application of harmonious mineral processing technology and new mineral processing agents and combined agents.

[0005] Invention patent CN201710201559.4 A low-cost, high-leaching-rate high-sulfur cobalt-copper ore treatment process discloses treating high-sulfur cobalt-copper ore by chemical metallurgy. Although good copper and cobalt yields can be obtained, on the one hand, the low-grade polymetallic sulfide ore treated by the present invention has a small content of useful minerals, and the energy consumption and reagent dosage required for chemical metallurgy are large. On the other hand, the equipment required for chemical metallurgy is high, and the investment and return are disproportionate.

[0006] Invention patent CN 110038730A discloses a beneficiation method for copper-cobalt sulfide ore containing two types of cobalt-containing minerals, which discloses first capturing the copper-cobalt rough concentrate, then flotation to obtain the copper-cobalt concentrate, and during the process recovering cobalt from the tailings and middlings. The method not only processes high-grade copper-cobalt sulfide ore, but also essentially recovers cobalt from the tailings, and does not involve effective separation of copper and cobalt.

[0007] Invention patent CN117599960A discloses a flotation separation agent and application of copper-cobalt waste rock, and discloses a flotation method for copper-cobalt waste rock, and finally obtains sulfur-cobalt concentrate and copper concentrate. Although the yields of sulfur-cobalt concentrate and copper concentrate are relatively high, the effective separation of sulfur and cobalt is not achieved, and the economic value of mineral processing still needs to be improved. Summary of the invention

[0008] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a cascade comprehensive recovery process for low-grade polymetallic sulfide ores.

[0009] The object of the present invention is achieved through the following technical scheme: a cascade comprehensive recovery process of low-grade polymetallic sulfide ore, comprising the following steps:

[0010] S1. Grinding: Grind the low-grade polymetallic sulfide ore to obtain a floating sample with a particle size of -0.074 mm and a content of 80% to 90%;

[0011] S2, copper roughing: 800-1000 g / t of pulp pH adjusting agent, 800-1000 g / t of sulfur combination inhibitor, 50-80 g / t of collector and 30-50 g / t of frother are sequentially added to the flotation sample, and roughing is performed after slurry adjustment to obtain copper rough concentrate and copper roughing tailings;

[0012] S3, copper concentration: adding 80-150 g / t of sulfur combination inhibitor to the copper rough concentrate for secondary concentration to obtain copper concentrate and concentrated middlings;

[0013] S4, copper scavenging: adding 100-200 g / t of sulfur combined inhibitor and 25-40 g / t of collector to the copper rougher tailings for one scavenging to obtain scavenging tailings and scavenging crude oil;

[0014] S5, sulfur-cobalt mixed flotation: 500-700 g / t of activator, 190-280 g / t of combined collector and 40-50 g / t of frother are sequentially added to the scavenging tailings to carry out sulfur-cobalt mixed flotation to obtain sulfur-cobalt concentrate and mixed flotation tailings;

[0015] S6, sulfur and cobalt separation flotation: 500-600 g / t of pulp pH adjuster, 300-500 g / t of sulfur-cobalt separation inhibitor and 40-55 g / t of frother are sequentially added to the sulfur-cobalt concentrate to carry out sulfur-cobalt separation flotation to obtain cobalt concentrate and sulfur concentrate;

[0016] Among them, the sulfur combination inhibitor is composed of tannin, citric acid and ammonium silicate in a mass ratio of 1:1:1 to 2:1:1, the collector is ethylthiocarbamate, the foaming agent is propylene glycol ethyl ether, the combined collector is amyl xanthate and butyl ammonium black medicine in a mass ratio of 5:1 to 2:1, and the sulfur-cobalt separation inhibitor is composed of sodium bisulfite and disodium ethylenediaminetetraacetic acid in a mass ratio of 2:1 to 4:1.

[0017] Furthermore, the copper grade of the low-grade polymetallic sulfide ore is 0.2-0.4%, the sulfur grade is 2.5-5%, and the cobalt grade is 0.008-0.02%.

[0018] Furthermore, in step S5, 190-280 g / t of combined collector and 15-20 g / t of frother are sequentially added to the mixed flotation tailings for one scavenging to obtain final tailings.

[0019] Furthermore, in step S6, the sulfur-cobalt separation flotation method includes separation roughing, primary separation concentrating and primary separation scavenging, and the ore in each operation is returned to the previous operation.

[0020] Furthermore, in step S5, the slurry pH adjuster is used in the separation roughing step; the sulfur-cobalt separation inhibitor is used in an amount of 200-300 g / t in the separation roughing step, and in an amount of 100-200 g / t in the separation concentration step; the foaming agent is used in an amount of 30-40 g / t in the separation roughing step, and in an amount of 10-15 g / t in the separation scavenging step.

[0021] Furthermore, the slurry pH adjuster is carbide slag, and the activator is copper sulfate.

[0022] The beneficial effects of the present invention are:

[0023] 1. The present invention targets polar-grade copper polymetallic ores, adopts a new cascade separation process of "copper priority flotation - sulfur-cobalt mixed flotation - sulfur-cobalt flotation separation", adds appropriate flotation reagents, obtains a stable flotation effect under weakly alkaline conditions of the ore pulp, recycles solid waste, and realizes green and low-carbon cascade comprehensive recovery of low-grade copper-cobalt polymetallic sulfide ores, especially the effective recovery of associated cobalt minerals in the ore.

[0024] 2. In order to achieve the recovery of cobalt, the sulfur-cobalt mixed concentrate is separated under the alkaline conditions formed by carbide slag (pH 9-10). The present invention innovatively uses sodium bisulfite + disodium ethylenediaminetetraacetic acid as separation inhibitors to achieve precise enrichment of cobalt-containing minerals (the enrichment ratio of cobalt to the original ore reaches more than 17) to obtain high-grade cobalt concentrate.

[0025] 3. When the present invention preferentially selects copper, it adopts the alkaline condition (pH 9-10) formed by carbide slag, creatively adopts sulfur combination inhibitor: tannin + citric acid + ammonium silicate, realizes efficient separation and recovery of copper, and obtains copper concentrate with a copper grade greater than 18% (the enrichment ratio of the original copper ore reaches more than 50). Among them, tannin is a gelling inhibitor, which mainly achieves the inhibitory effect by adsorbing on the surface of pyrite and pyrrhotite to form a protective film, citric acid is a carboxylic acid small molecule inhibitor, which mainly achieves the inhibitory effect by forming hydroxyl or carboxyl coordination with the surface of pyrite and pyrrhotite, and ammonium silicate is a silicate inhibitor, which mainly achieves the inhibitory effect by forming a silicon oxide film on the surface of pyrite and pyrrhotite. Through the combined synergistic inhibitory effect of the three inhibitors, the floating of pyrite and pyrrhotite can be better controlled during copper selection.

[0026] 4. The small molecule foaming agent of the present invention has strong activity, the foam formed is brittle, the mineralization effect is good, and the synergistic performance with the inhibitor and the collector is excellent.

[0027] 5. The process of the present invention is stable and reliable, and can obtain a stable flotation separation effect under weakly alkaline conditions, with excellent separation indicators. It is an ideal comprehensive recovery method for copper polymetallic ores. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a flow chart of the principle of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0030] Example 1

[0031] 1. Ore characteristics:

[0032] A low-grade copper ore in a certain place has a copper grade of 0.35%, a sulfur grade of 3.52%, and a cobalt content of 0.014%. The main sulfides in the ore are pyrite, pyrrhotite and chalcopyrite, and the gangue minerals are mainly actinolite, pyroxene and calcite. Studies on the properties of the ore show that the chalcopyrite is embedded in a fine particle size, and the original ore needs to be finely ground to fully dissociate the copper mineral monomer. The carrier mineral of the cobalt element in the ore is pyrite.

[0033] In the early stage, the main problems in the on-site production of the mine were: due to the high cost of the related reagents used and the lack of new reagents for sulfur-cobalt separation, the associated cobalt minerals and pyrite were not efficiently and comprehensively recovered.

[0034] 2. Ore dressing process:

[0035] (1) Grind the raw ore to obtain a floating sample with a particle size of -0.074 mm and a content of 85.8%;

[0036] (2) sequentially adding a pulp pH adjuster, a sulfur combination inhibitor, a collector, and a frother to the flotation sample of step (1), and performing roughing after slurry adjustment to obtain a copper rough concentrate and a copper roughing tailing;

[0037] (3) adding a sulfur combination inhibitor to the sulfur rough concentrate obtained in step (2) and then performing a second cleaning; adding a sulfur combination inhibitor and a collector to the copper rougher tailings and then performing a scavenging; the ore in each operation is returned to the previous operation in sequence;

[0038] (4) adding an activator, a combined collector and a frother to the scavenging tailings obtained in step (3) in sequence to carry out sulfur-cobalt mixed flotation to obtain a sulfur-cobalt concentrate and a mixed flotation tailings; adding a combined collector and a frother to the mixed flotation tailings in sequence to carry out a sulfur-cobalt mixed flotation scavenging to obtain a final tailings;

[0039] (5) adding a pulp pH adjuster, a separation inhibitor and a frother to the sulfur-cobalt concentrate obtained in step (4) in sequence, and then performing sulfur-cobalt separation flotation, including separation roughing, primary separation concentrating and primary separation scavenging, to obtain cobalt concentrate and sulfur concentrate; the ore in each operation is returned to the previous operation in sequence.

[0040] The slurry pH adjuster is solid waste carbide slag; the sulfur combination inhibitor is composed of three components: tannin, citric acid, and ammonium silicate, and the mass ratio of the three is 1:1:1; the sulfur-cobalt separation inhibitor is composed of sodium bisulfite and disodium ethylenediaminetetraacetic acid, and the mass ratio of the two is 2:1; the foaming agent for sulfur-cobalt mixed flotation and sulfur-cobalt separation is propylene glycol ethyl ether.

[0041] In steps (2) to (3), the copper flotation collector is ethylthiocarbamate; wherein the amount of ethylthiocarbamate used in the copper roughing process is 55 g / t of the ore, and the amount of ethylthiocarbamate used in the copper scavenging process is 30 g / t of the ore.

[0042] In steps (2) to (3), the amount of carbide slag, a slurry pH adjuster for copper roughing, used in copper roughing is 900 g / t of ore; the amount of sulfur combination inhibitor used in copper roughing is 900 g / t of ore, the amount used in copper scavenging is 100 g / t of ore, and the amount used in copper concentration 1 is 100 g / t.

[0043] In steps (4) to (5), the activator for sulfur-cobalt mixed flotation is copper sulfate, and its usage in sulfur-cobalt mixed flotation is 600 g / t of raw ore; the combined collectors are amyl xanthate and butyl ammonium black powder, and their usage in sulfur-cobalt mixed flotation is 150 g / t of raw ore and 50 g / t of raw ore, respectively; the amyl xanthate and butyl ammonium black powder are used in sulfur-cobalt mixed scavenging at 160 g / t of raw ore and 50 g / t of raw ore, respectively; the propylene glycol ethyl ether, a frother for sulfur-cobalt mixed flotation, is used in sulfur-cobalt mixed roughing at 40 g / t of raw ore and in sulfur-cobalt mixed scavenging at 15 g / t of raw ore.

[0044] In steps (4) to (5), the pH adjuster of the slurry for sulfur-cobalt separation flotation is carbide slag, and its usage in sulfur-cobalt separation roughing is 500 g / t of original ore; the sulfur-cobalt separation inhibitor is used in sulfur-cobalt separation roughing at 200 g / t of original ore, and in sulfur-cobalt separation fine separation at 100 g / t of original ore; the foaming agent propylene glycol ethyl ether is used in sulfur-cobalt separation roughing at 30 g / t of original ore, and in sulfur-cobalt separation scavenging at 10 g / t of original ore.

[0045] 3. Flotation separation test indicators:

[0046] According to the ore characteristics, on the basis of detailed condition tests, the above-mentioned beneficiation method was used to obtain excellent technical indicators. The results are shown in Table 1.

[0047] Table 1

[0048] Product Name grade(%) Recovery rate (%) Copper Concentrate Copper 17.14 Copper 80.51 Cobalt Concentrate Cobalt 0.24 Cobalt 52.29 Sulfur concentrate Sulfur 38.15 Sulfur 67.81

[0049] Example 2

[0050] The ore characteristics are the same as those in Example 1, and the ore dressing process is as follows:

[0051] (1) Grind the raw ore to obtain a floating sample with a particle size of -0.074 mm and a content of 89.4%;

[0052] (2) sequentially adding a pulp pH adjuster, a sulfur combination inhibitor, a collector, and a frother to the flotation sample of step (1), and performing roughing after slurry adjustment to obtain a copper rough concentrate and a copper roughing tailing;

[0053] (3) adding a sulfur combination inhibitor to the sulfur rough concentrate obtained in step (2) and then performing a second cleaning; adding a sulfur combination inhibitor and a collector to the copper rougher tailings and then performing a scavenging; the ore in each operation is returned to the previous operation in sequence;

[0054] (4) adding an activator, a combined collector and a frother in sequence to the scavenging tailings obtained in step (3) to carry out sulfur-cobalt mixed flotation to obtain a sulfur-cobalt concentrate and a mixed flotation tailings; adding a combined collector and a frother in sequence to the mixed flotation tailings to carry out a scavenging to obtain a final tailings;

[0055] (5) adding a pulp pH adjuster, a separation inhibitor and a frother to the sulfur-cobalt concentrate obtained in step (4) in sequence, and then performing sulfur-cobalt separation flotation, including separation roughing, primary separation concentrating and primary separation scavenging, to obtain cobalt concentrate and sulfur concentrate; the ore in each operation is returned to the previous operation in sequence.

[0056] The slurry pH adjuster is solid waste carbide slag; the sulfur combination inhibitor is composed of tannin, citric acid, and ammonium silicate, and the mass ratio of the three is 2:1:1; the sulfur-cobalt separation inhibitor is composed of sodium bisulfite and disodium ethylenediaminetetraacetic acid, and the mass ratio of the two is 4:1; the foaming agent for sulfur-cobalt mixed flotation and sulfur-cobalt separation is propylene glycol ethyl ether.

[0057] In steps (2) to (3), the copper flotation collector is ethylthiocarbamate; wherein the amount of ethylthiocarbamate used in the copper roughing process is 80 g / t of the ore, and the amount of ethylthiocarbamate used in the copper scavenging process is 40 g / t of the ore.

[0058] In steps (2) to (3), the amount of carbide slag, a slurry pH adjuster for copper roughing, used in copper roughing is 900 g / t of ore; the amount of sulfur combination inhibitor used in copper roughing is 1000 g / t of ore, the amount used in copper scavenging is 200 g / t of ore, and the amount used in copper concentration 1 is 150 g / t.

[0059] In steps (4) to (5), the activator for sulfur-cobalt mixed flotation is copper sulfate, and its usage in sulfur-cobalt mixed roughing is 700 g / t of raw ore; the collectors for sulfur-cobalt mixed flotation are amyl xanthate and butyl ammonium black powder, and their usage in sulfur-cobalt mixed roughing is 200 g / t of raw ore and 80 g / t of raw ore respectively; the usage of amyl xanthate and butyl ammonium black powder in sulfur-cobalt mixed scavenging is 200 g / t of raw ore and 80 g / t of raw ore respectively; the frother propylene glycol ethyl ether is used in sulfur-cobalt mixed roughing at 50 g / t of raw ore and in sulfur-cobalt mixed scavenging at 20 g / t of raw ore.

[0060] In steps (4) to (5), the pH adjuster of the slurry for sulfur-cobalt separation flotation is carbide slag, and its usage in sulfur-cobalt separation roughing is 600 g / t of original ore; the sulfur-cobalt separation flotation depressant is used in sulfur-cobalt separation roughing is 300 g / t of original ore, and its usage in sulfur-cobalt separation fine separation is 200 g / t of original ore; the sulfur-cobalt separation flotation frother is propylene glycol ethyl ether, and its usage in sulfur-cobalt separation roughing is 40 g / t of original ore, and its usage in sulfur-cobalt separation scavenging is 15 g / t of original ore.

[0061] According to the ore characteristics, on the basis of detailed condition tests, the above-mentioned beneficiation method was used to obtain excellent technical indicators. The results are shown in Table 2.

[0062] Table 2

[0063] Product Name grade(%) Recovery rate (%) Copper Concentrate Copper 18.10 Copper 77.84 Cobalt Concentrate Cobalt 0.25 Cobalt 50.87 Sulfur concentrate Sulfur 40.52 Sulfur 65.87

[0064] Comparative Example 1

[0065] The ore characteristics of Comparative Example 1 are the same as those of Example 1, and the ore dressing process adopts the flotation separation reagent of copper-cobalt waste rock in patent CN117599960A and the method described in Example 1 in the application. The technical index results are shown in Table 3.

[0066] Table 3

[0067]

[0068] Compared with the flotation separation agent and application of copper-cobalt waste rock in patent CN117599960A, the present invention focuses on the innovative application of sulfur combination inhibitors in copper selection and the innovative application of sulfur-cobalt separation inhibitors in the separation of sulfur-cobalt mixed concentrates, thereby achieving efficient copper-sulfur separation and separation of sulfur-cobalt mixed concentrates, and obtaining three concentrate products: copper concentrate, cobalt concentrate and sulfur concentrate.

[0069] Comparative Example 2 (Using Conventional Sulfur Combination Inhibitor)

[0070] The ore characteristics and mineral processing method of Comparative Example 2 are the same as those of Example 1, with the only difference being that in Comparative Example 2, the sulfur combination inhibitors tannin, citric acid, and ammonium silicate (mass ratio 1:1:1) are replaced by conventional sulfur inhibitor sodium humate. The technical index results are shown in Table 4.

[0071] Comparative Example 3 (Using conventional sulfur combination inhibitor)

[0072] The ore characteristics and mineral processing method of Comparative Example 3 are the same as those of Example 1, with the only difference being that in Comparative Example 3, the sulfur combination inhibitors tannin, citric acid, and ammonium silicate (mass ratio 1:1:1) are replaced by conventional sulfur inhibitor sodium sulfate. The technical index results are shown in Table 4.

[0073] Table 4

[0074]

[0075] Comparative Example 4 (Using Conventional Sulfur-Cobalt Separation Inhibitor)

[0076] The ore characteristics and mineral processing method of Comparative Example 4 are the same as those of Example 1, with the only difference being that in Comparative Example 4, the sulfur-cobalt separation inhibitors sodium bisulfite and disodium ethylenediaminetetraacetate (mass ratio 2:1) are replaced by conventional sulfur-cobalt separation inhibitor sodium thioglycolate. The technical index results are shown in Table 5.

[0077] Comparative Example 5 (Using Conventional Sulfur-Cobalt Separation Inhibitor)

[0078] The ore characteristics and mineral processing method of Comparative Example 5 are the same as those of Example 1, except that in Comparative Example 5, the sulfur-cobalt separation inhibitors sodium bisulfite and disodium ethylenediaminetetraacetate (mass ratio 2:1) are replaced by conventional sulfur-cobalt separation inhibitor carboxymethyl cellulose. The technical index results are shown in Table 5.

[0079] Table 5

[0080]

[0081]

[0082] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A cascade comprehensive recovery process for low-grade polymetallic sulfide ores, characterized in that: The following steps are involved: S1. Grinding: Grind the low-grade polymetallic sulfide ore to obtain a floating sample with a particle size of -0.074 mm and a content of 80% to 90%; S2, copper roughing: 800-1000 g / t of pulp pH adjusting agent, 800-1000 g / t of sulfur combination inhibitor, 50-80 g / t of collector and 30-50 g / t of frother are sequentially added to the flotation sample, and roughing is performed after slurry adjustment to obtain copper rough concentrate and copper roughing tailings; S3, copper concentration: adding 80-150 g / t of sulfur combined inhibitor to the copper rough concentrate for secondary concentration to obtain copper concentrate and concentrated middlings; S4, copper scavenging: adding 100-200 g / t of sulfur combined inhibitor and 25-40 g / t of collector to the copper rougher tailings for one scavenging to obtain scavenging tailings and scavenging crude oil; S5, sulfur-cobalt mixed flotation: 500-700 g / t of activator, 190-280 g / t of combined collector and 40-50 g / t of frother are sequentially added to the scavenging tailings to carry out sulfur-cobalt mixed flotation to obtain sulfur-cobalt concentrate and mixed flotation tailings; S6, sulfur and cobalt separation flotation: 500-600 g / t of pulp pH adjuster, 300-500 g / t of sulfur-cobalt separation inhibitor and 40-55 g / t of frother are sequentially added to the sulfur-cobalt concentrate to carry out sulfur-cobalt separation flotation to obtain cobalt concentrate and sulfur concentrate; Among them, the sulfur combination inhibitor is composed of tannin, citric acid and ammonium silicate in a mass ratio of 1:1:1 to 2:1:1, the collector is ethylthiocarbamate, the foaming agent is propylene glycol ethyl ether, the combined collector is amyl xanthate and butyl ammonium black medicine in a mass ratio of 5:1 to 2:1, and the sulfur-cobalt separation inhibitor is composed of sodium bisulfite and disodium ethylenediaminetetraacetic acid in a mass ratio of 2:1 to 4:

1.

2. The cascade comprehensive recovery process of low-grade polymetallic sulfide ore according to claim 1, characterized in that: The low-grade polymetallic sulfide ore has a copper grade of 0.2-0.4%, a sulfur grade of 2.5-5%, and a cobalt grade of 0.008-0.02%.

3. The cascade comprehensive recovery process of low-grade polymetallic sulfide ore according to claim 1, characterized in that: In step S5, 190-280 g / t of combined collector and 15-20 g / t of frother are sequentially added to the mixed flotation tailings for one scavenging to obtain final tailings.

4. The cascade comprehensive recovery process of low-grade polymetallic sulfide ore according to claim 1, characterized in that: In step S6, the sulfur-cobalt separation flotation method includes separation roughing, primary separation concentrating and primary separation scavenging, and the ore in each operation is returned to the previous operation.

5. The cascade comprehensive recovery process of low-grade polymetallic sulfide ore according to claim 4, characterized in that: In step S6, the slurry pH adjuster is used in the separation roughing step; the sulfur-cobalt separation inhibitor is used in an amount of 200-300 g / t in the separation roughing step, and in an amount of 100-200 g / t in the separation concentration step; the foaming agent is used in an amount of 30-40 g / t in the separation roughing step, and in an amount of 10-15 g / t in the separation scavenging step.

6. The cascade comprehensive recovery process of low-grade polymetallic sulfide ore according to claim 1, characterized in that: The slurry pH adjuster is carbide slag, and the activator is copper sulfate.

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