A serpentine inhibitor, a high-efficiency flotation method for high-serpentine nickel sulfide ore

Abstract

The present invention discloses a serpentine inhibitor and an efficient flotation method for high-serpentine nickel sulfide ore. The serpentine inhibitor is composed of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, diethylenetriamine penta (methylene phosphonic acid) and xanthan gum in a mass ratio of 60-30:40-20:25-10. The method for efficiently separating high-serpentine nickel sulfide ore comprises the steps of: grinding the raw ore; adding a serpentine inhibitor and a collector to the ore pulp, and performing a flotation process of one to two roughing, three scavenging, and two cleaning, regrinding the rough concentrate, and sequentially returning the middlings to obtain nickel concentrate and flotation tailings. The new separation method provided by the present invention can achieve efficient separation of high-serpentine nickel sulfide ore. When the raw ore contains Cu 0.1-0.5%, Ni 0.5-1.2%, and MgO 15-35%, the nickel concentrate can have a magnesium oxide grade of ≤6%, a copper recovery rate of ≥70%, and a nickel recovery rate of ≥72%.

Description

Technical Field

[0001] The invention belongs to the technical field of mineral processing, and in particular relates to a serpentine inhibitor and an efficient flotation method for high-serpentine nickel sulfide ore. Background Art

[0002] Nickel metal, with its exceptional properties of energy storage, corrosion resistance, wear resistance, high temperature resistance, and high strength, is a key raw material in industries such as stainless steel, electroplating, and high-temperature alloys, and is crucial for the development of the national economy. As a key metal in new energy vehicle batteries, nickel is facing increasing demand, and nickel resources are in short supply, resulting in my country's high dependence on foreign nickel resources. Therefore, the efficient utilization of nickel resources is crucial for my country's new materials and new energy industries.

[0003] 90% of my country's nickel ore resources are nickel sulfide ores. The formation of most nickel sulfide deposits is related to the magmatic activity of basic or ultrabasic rocks. The main gangue minerals are magnesium-iron-calcium silicates. During the mineralization process, intense alteration occurs, forming gangue minerals such as serpentine, which are classified as serpentine-bearing nickel sulfide ores. Due to the opposite surface charges of serpentine and pentlandite, their close coexistence, the uneven distribution of pentlandite particles, and the susceptibility of serpentine to mud during grinding, serpentine covers the pentlandite surface during the separation process, seriously interfering with the flotation of the pentlandite. Efficient flotation separation of serpentine and nickel sulfide ores is key to the efficient recovery of my country's nickel metal resources.

[0004] According to nickel flash smelting technology, the MgO content in nickel concentrate must be controlled below 6.8%. Excessive MgO content increases slag viscosity, raises the slag melting point, and reduces smelting recovery. For example, at the Jinchuan Nickel Mine, a large nickel sulfide deposit accounting for over 80% of China's total nickel reserves and production, the serpentine content in the raw ore is as high as 46%. Taking the rich ore from the second mining area and the lean ore from the third mining area of ​​the Jinchuan Nickel Mine as examples, the on-site process follows a principle of "coarse grinding of raw ore (-0.074mm, accounting for approximately 65%), followed by regrinding and selection of tailings (-0.074mm, accounting for approximately 81%). Only collectors are added throughout the selection process, without inhibitors. Furthermore, ball milling is currently used for the secondary grinding of copper-nickel ore. This results in a wide particle size distribution of useful copper and nickel minerals in the milled product, leading to severe over-grinding. This makes it difficult to recover fine nickel particles and difficult to control argillaceous gangue such as serpentine, resulting in a total nickel concentrate with a magnesium oxide content exceeding 12%.

[0005] To address these challenges, existing research focuses on the development and application of highly effective serpentine inhibitors, without changing existing processes. CN 116159680A provides a serpentine inhibitor, nanocellulose; CN 117531607A provides carboxymethyl cellulose or a mixture of carboxymethyl cellulose and sodium alginate as a serpentine inhibitor; CN 112934473 A provides a serpentine inhibitor comprising an organophosphate compound, an organic acid polymer, and hydroxypropyl starch; and CN 116441058 A employs a complexing agent-combination inhibitor-adjusting agent-collecting agent-foaming agent method to reduce the magnesium oxide content in concentrates. The combination inhibitor comprises inhibitor type 1 (one of sodium hexametaphosphate, carboxymethyl cellulose, starch, or water glass) and inhibitor type 2 (one of lignin sulfonate, guar gum, or chitosan). A small number of studies have also been conducted on the optimization of the beneficiation process and grinding equipment for high-serpentine sulfide copper-nickel ores. Among them, CN115445777A adopts stage grinding and stage selection, and regrinds the primary mixed roughing tailings and middlings, with a regrinding fineness of -0.074mm greater than 93%; CN115301399 A adopts three-stage grinding, with the first stage using semi-autogenous grinding, the second stage using ball milling, and the third stage using sand milling. The overflow product content of the third hydrocyclone with a particle size of -0.074mm is more than 90%; CN115672539 A adopts a one-stage coarse grinding-tailings regrinding process, with a regrinding fineness of -0.038mm accounting for 75-85%. Clearly, existing research on the separation of serpentine-containing nickel sulfide ores has improved the separation index of pentlandite by focusing on inhibitor development, process optimization, and grinding equipment improvement. While some progress has been made, the problem of high MgO content in high-serpentine nickel sulfide ore concentrates has not been fundamentally resolved. Analyzing the existing separation process, the process of primary coarse grinding followed by tailings regrinding is long and complex, with high grinding energy consumption during tailings regrinding. The high-grade nickel concentrate obtained during primary separation has a high MgO content due to insufficient pentlandite dissociation. While tailings regrinding does indeed facilitate the dissociation of fine-grained pentlandite, it also dramatically increases the mudification of other gangues, such as serpentine, leading to the circulation of muddy gangue in the separation system. Even with the use of newly developed, highly efficient serpentine inhibitors, the reduction in MgO content in the low-grade nickel concentrate obtained through re-selection is still limited. Therefore, it is urgent to optimize the new method for the selection of this type of ore based on the embedded particle size characteristics of pentlandite aggregates in high-serpentine nickel sulfide ores, from the two aspects of process optimization and the development of efficient serpentine inhibitors, and realize the efficient recovery and utilization of this type of nickel ore resources. Summary of the Invention

[0006] The present invention aims to address the difficulties in separating high-serpentine nickel sulfide ores and provide a serpentine inhibitor and a method for efficiently separating high-serpentine nickel sulfide ores. The method is used to solve the problems in the flotation system of such ores, such as the cumbersome process caused by tailings regrinding, high grinding energy consumption, difficulty in suppressing serpentine after grinding, and excessive MgO content in the concentrate.

[0007] To achieve the above objectives, the present invention provides the following technical solutions:

[0008] The serpentine inhibitor (PD) provided by the present invention is composed of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer (AA / AMPS), diethylenetriaminepenta(methylenephosphonic acid) (DTPMPA) and xanthan gum (XG), wherein the mass ratio of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, diethylenetriaminepenta(methylenephosphonic acid) and xanthan gum is (60-30):(40-20):(25-10).

[0009] The AA / AMPS is prepared by copolymerization of acrylic acid and 2-methylpropanesulfonic acid.

[0010] The application of the PD in the flotation of high serpentine nickel sulfide ore.

[0011] The present invention also provides a method for efficiently separating high-serpentine nickel sulfide ore, comprising the following steps:

[0012] 1) Ore grinding: After the ore is crushed, it is wet-milled to obtain flotation slurry;

[0013] 2) Roughing: transferring the incoming flotation pulp into a flotation tank, adding the serpentine inhibitor PD, ethyl xanthate, and butyl ammonium nitrosulfate to the pulp, and performing roughing operations to obtain nickel roughing concentrate and roughing tailings, respectively;

[0014] 3) Regrinding the rougher concentrate: Regrinding the nickel rougher concentrate to obtain a reground rougher concentrate slurry;

[0015] 4) Concentration: Add the serpentine inhibitor PD to the regrinded rougher concentrate slurry to perform concentrating operations to obtain concentrate and middlings; the middlings are returned to the previous flotation operation;

[0016] 5) Scavenging: Add ethyl xanthate and butyl ammonium nitrosulfate to the roughing tailings for scavenging to obtain scavenging concentrate and tailings; the scavenging concentrate is returned to the previous flotation operation.

[0017] The relative content of serpentine in the high-serpentine nickel sulfide ore of the present invention is generally above 20%.

[0018] Preferably, in step 1), after the raw ore is crushed, wet ball milling is performed, and the grinding fineness is -0.074 mm, accounting for 75-85%, so that the pentlandite aggregate and the gangue minerals are fully dissociated to obtain the flotation slurry;

[0019] Preferably, in step 2), the roughing operation is one or two roughing operations:

[0020] When the roughing operation is a single roughing operation, the specific process flow is as follows: first add PD 200-700g / t, stir for 2-3 minutes; then add ethyl xanthate 50-300g / t, stir for 2-3 minutes; then add butyl ammonium black powder 20-100g / t, stir for 2-3 minutes, perform roughing operation, scrape and foam for 2-5 minutes, and obtain nickel roughing concentrate and roughing tailings respectively;

[0021] When the roughing operation is secondary roughing, the specific steps are:

[0022] Roughing 1: first add PD 200-700g / t, stir for 2-3 minutes; then add ethyl xanthate 50-300g / t, stir for 2-3 minutes; then add butyl ammonium nitrosulfate 20-100g / t, stir for 2-3 minutes, and then carry out roughing 1 operation. Scrape and foam for 2-5 minutes to obtain nickel roughing 1 concentrate and roughing 1 tailings respectively;

[0023] Roughing II: first add 50-200g / t of PD to the roughing I tailings and stir for 2-3 minutes; then add 25-150g / t of ethyl xanthate and stir for 2-3 minutes; then add 10-50g / t of butyl ammonium black powder and stir for 2-3 minutes, and carry out the roughing II operation. Scrape and foam for 2-5 minutes to obtain nickel roughing II concentrate and roughing II tailings respectively; the nickel roughing I concentrate and nickel roughing II concentrate are combined into nickel roughing concentrate.

[0024] Preferably, in step 3), the nickel rougher concentrate is ground again to a fineness of -0.038 mm, accounting for 70-85%.

[0025] Preferably, in step 4), the selection operation is performed twice, specifically:

[0026] Copper Concentration 1: Add 100-300g / t of PD to the regrinding rougher concentrate slurry and stir for 2-3 minutes to carry out copper concentration 1 to obtain copper concentration 1 concentrate and copper concentration middlings 1; copper concentration middlings 1 are returned to the rougher concentration 1;

[0027] Concentration 2: Blank concentration is performed on the copper concentrate 1 to obtain nickel concentrate and nickel concentrate middlings 2; the nickel concentrate middlings 2 are returned to the concentration 1 operation.

[0028] Preferably, in step 5), the scanning operation is performed three times, specifically:

[0029] Scavenging 1: Add 25-150g / t of ethyl xanthate to the roughing tailings, stir for 2-3 minutes, add 10-50g / t of butyl ammonium nitrosulfate, stir for 2-3 minutes, carry out scavenging 1, scrape and foam for 1-3 minutes to obtain nickel scavenging 1 concentrate and nickel scavenging 1 tailings respectively; the nickel scavenging 1 concentrate is returned to the roughing 1 operation;

[0030] Scavenging 2: Add 13-75g / t of ethyl xanthate to the nickel scavenging 1 tailings, stir for 2-3 minutes, add 10-50g / t of butyl ammonium black powder, stir for 2-3 minutes, carry out scavenging 2 operation, scrape and foam for 1-3 minutes to obtain nickel scavenging 2 concentrate and nickel scavenging 2 tailings respectively; the nickel scavenging 2 concentrate is returned to the scavenging 1 operation;

[0031] Scavenging and selection three: add 10-40g / t of ethyl xanthate to the nickel scavenging and selection two tailings, stir for 2-3 minutes, carry out scavenging and selection three operation, scrape and foam for 1-3 minutes, and obtain nickel scavenging and selection three concentrate and tailings respectively; the nickel scavenging and selection three concentrate is returned to the scavenging and selection two operation.

[0032] Preferably, the serpentine inhibitor PD is added by first preparing AA / AMPS, DTPMPA, and XG into aqueous solutions, wherein the mass concentration of AA / AMPS is 1-5%, the mass concentration of DTPMPA is 1-5%, and the mass concentration of XG is 0.5-1%, and then adding the above aqueous solutions together to the slurry.

[0033] Principle of the present invention:

[0034] For high-serpentine nickel sulfide ores, the selection process presents the problem of serpentine seriously interfering with the flotation of nickel sulfide ores. Existing technologies typically employ a "coarse grinding of the ore - regrinding and reselection of the tailings" process. After coarse grinding of the ore, a selection stage is performed. While some pentlandite can be selected, the low degree of dissociation of the pentlandite monomer results in a high magnesium oxide content in the obtained nickel concentrate 1. While regrinding the tailings can dissociate fine-grained pentlandite, it also exacerbates the mudification of gangue such as serpentine. Traditional inhibitors have poor complete inhibition effects on fine-grained serpentine, and fine-grained serpentine enters the nickel concentrate 2 through heterogeneous agglomeration and mechanical entrainment, resulting in a high MgO content in the concentrate. Based on the interbedded particle size characteristics of pentlandite aggregates in high-serpentine nickel sulfide ores, the present invention designs and proposes a shortened separation process consisting of "raw ore grinding, coarse concentrate regrinding, and then selection." The raw ore is ground to a fineness that separates the pentlandite aggregate from the gangue, while some tailings (primarily serpentine and other gangue that are easily muddied) are discarded to ensure nickel recovery. The pentlandite aggregate is then regrinded to dissociate into monomers. Based on this, a highly efficient inhibitor, PD, which selectively adsorbs serpentine, is added to achieve efficient flotation recovery of the pentlandite, yielding a high-grade pentlandite concentrate. The present invention utilizes a single-stage grinding process to dissociate the pentlandite aggregate and then adds the PD inhibitor, pre-removing some serpentine and other gangue, preventing them from circulating continuously throughout the flotation system and affecting nickel flotation. Based on the flotation velocity of the pentlandite in the raw ore, a single or double roughing process is designed to allow the pentlandite aggregate to float cleanly into the coarse concentrate, ensuring nickel recovery. The second-stage coarse concentrate is re-grinded with pentlandite aggregate, which has a small amount of grinding and low grinding energy consumption. The inhibitor PD is added after the coarse concentrate is re-grinded for beneficiation, which is beneficial to improving the nickel grade of the concentrate.

[0035] Compared with the original process of tailings regrinding, the process of coarse concentrate regrinding in the present invention is simple, the grinding energy consumption is low, and while ensuring a high nickel recovery rate in nickel concentrate, it is more conducive to reducing magnesium in nickel concentrate. In addition to process innovation, the present invention also provides a high-efficiency combined inhibitor PD for serpentine, which is composed of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer (AA / AMPS), diethylenetriamine penta (methylene phosphonic acid) (DTPMPA), and xanthan gum (XG). The molecular structure of AA / AMPS contains carboxyl groups with good dispersibility and sulfonic acid groups with strong polarity. On the one hand, AA / AMPS can better disperse the ore pulp; on the other hand, carboxyl groups and sulfonic acid groups are the basis for coordination with metal ions to form complexes. Therefore, AA / AMPS has polar groups with spatial arrangement positions suitable for chelating with Mg on the mineral surface. It is adsorbed on the serpentine surface through complexation (or chelation) with the metal cation Mg ions on the serpentine surface lattice. It also has sufficient hydrophilic groups, which greatly improves the hydrophilicity of the serpentine surface. DTPMPA contains phosphonic acid groups in its molecular structure. Based on the dehydration condensation mechanism, DTPMPA provides protons as a Brønsted acid, while the hydroxylated mineral surface provides hydroxyl groups as a Brønsted base. Serpentine surfaces are rich in hydroxyl groups and are common alkaline metal oxide surfaces containing hydroxyl groups. The density of hydroxyl groups generated by oxidation on nickel sulfide surfaces is relatively low. Therefore, according to the Brønsted acid-base reaction, phosphonic acid groups are more likely to interact selectively with the serpentine surface. The combination of AA / AMPS and DTPMPA can both generate negatively charged species in the slurry system, which adsorb onto the serpentine surface, altering the serpentine surface potential and promoting heterogeneous dispersion of serpentine and nickel sulfide. Furthermore, their addition can reduce flotation slurry viscosity, minimize mechanical entrainment of fine-grained serpentine by froth, and reduce the MgO content in nickel concentrates. The high negative charge density macromolecular inhibitor SG can quickly neutralize the positive charge on the surface of serpentine in a complex flotation system, and flocculate fine-grained serpentine into large particles through macromolecular bridging, causing it to settle. At the same time, it is more conducive to the interaction of large-particle serpentine in the flocs with AA / AMPS and DTPMPA, synergistically strengthening the inhibition of serpentine.

[0036] Beneficial effects of the present invention:

[0037] 1. For the separation of high-serpentine nickel sulfide ores, this invention provides a shortened flotation process combining raw ore grinding with coarse concentrate regrinding and re-separation. This process, which employs PD as a serpentine depressant, enables efficient separation of such ores. For raw ore containing 0.1-0.5% Cu, 0.5-1.2% Ni, and 15-35% MgO, the novel separation method provided by this invention can achieve a nickel concentrate with a magnesium oxide grade of ≤6%, a copper recovery of ≥70%, and a nickel recovery of ≥72%.

[0038] 2. The novel serpentine inhibitor PD provided by this invention is composed of a combination of a polycarboxylic acid inhibitor, an organophosphine inhibitor, and a polymeric inhibitor, xanthan gum. It exhibits high selectivity and inhibitory properties against serpentine and other gangue materials. All three agents are water-soluble, making preparation simple and easy to incorporate into industrial applications. Furthermore, both the polycarboxylic acid inhibitor and the organophosphine inhibitor can complex heavy metal ions in wastewater, significantly reducing the difficulty of wastewater reuse. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flotation process flow chart of Example 1;

[0040] Figure 2 This is a flotation process flow chart of Comparative Example 9;

[0041] Figure 3 This is a flotation process flow chart of Comparative Example 10;

[0042] Figure 4 is a flotation process flow chart of Examples 2 and 3;

[0043] Figure 5 This is the flotation process flow chart of Comparative Example 14. DETAILED DESCRIPTION

[0044] In the following examples and comparative examples, all the drugs used can be purchased from commercial sources.

[0045] Example 1

[0046] A high-serpentine nickel sulfide ore was obtained from Gansu. The main valuable elements in the ore are copper and nickel, with a Cu grade of 0.28% and a Ni grade of 0.96%. The detrimental element As in the ore is less than 0.005%, which does not affect the quality of the concentrate. The SiO2 grade is 33.14%, Al2O3 grade is 2.61%, CaO grade is 2.55%, and MgO grade is 25.81%. XRD and mineral composition results show that the main sulfide minerals in the ore are pentlandite, chalcopyrite, pyrrhotite, and pyrite. The main gangue minerals are magnesium-containing silicate minerals such as serpentine and chlorite, and quartz. The sulfide minerals are mainly distributed in the gangue minerals as individual components or aggregates, interlocked with each other.

[0047] The raw ore sample is first crushed and ground to -0.074mm, accounting for 81%. Then the ground ore pulp is poured into the flotation tank for flotation test. The test process and reagent system are as follows: Figure 1 As shown. In this embodiment, all the reagent addition amounts are relative to the original ore. The specific steps are as follows:

[0048] In this embodiment, PD is composed of AA / AMPS (CAS No. 40623-75-4), DTPMPA, and XG (CAS No. 11138-66-2) in a mass ratio of 50:30:20. Before adding PD to the ore slurry, AA / AMPS, DTPMPA, and XG are prepared into 3% AA / AMPS aqueous solution, 3% DTPMPA aqueous solution, and 0.5% XG aqueous solution, respectively, and then all three aqueous solutions are added to the ore slurry.

[0049] The process flow in this embodiment adopts one coarse, three sweeps and two fines, and the coarse concentrate is re-grinded.

[0050] 1) Primary roughing: add 400g / t of PD to the ground slurry, stir for 2 minutes, add 150g / t of ethyl xanthate, stir for 2 minutes, add 40g / t of butyl ammonium black powder, stir for 2 minutes, aerate and flotate, scrape for 3 minutes, and the obtained foam product is the copper-nickel coarse concentrate. The product in the tank is the scavenging feed.

[0051] 2) Regrinding: The copper-nickel coarse concentrate is ball-milled and regrinded, and the grinding fineness is -0.038mm, accounting for 78%.

[0052] 3) Three scans

[0053] Scavenging 1: add 60g / t of ethyl xanthate to the scavenging 1 feed, stir for 2 minutes, add 10g / t of butyl ammonium nitrate, stir for 2 minutes, aerate and flotate, and scrape for 1.5 minutes to obtain scavenging 1 concentrate and scavenging 1 tailings;

[0054] Scavenging 2: Add 40g / t of ethyl xanthate to the scavenging 1 tailings, stir for 2 minutes, add 10g / t of butyl ammonium nitrate, stir for 2 minutes, aerate and flotate, and scrape for 1.5 minutes to obtain scavenging 2 concentrate and scavenging 2 tailings;

[0055] Scavenging and selection 3: add 20g / t of ethyl xanthate to the tailings of scavenging and selection 2, stir for 2 minutes, aerate and float, scrape and flot for 1.5 minutes to obtain scavenging and selection 3 concentrate and tailings;

[0056] 4) Two selections

[0057] Concentrated 1: Add 150g / t PD to the regrinded copper-nickel coarse concentrate, stir for 2 minutes, aerate and flotate, and scrape for 2 minutes to obtain concentrated ore and concentrated middlings.

[0058] Concentration II: blank concentration is carried out on the concentrate of Concentration I, aeration flotation, and scraping for 2 minutes to obtain concentrate and Concentration II middlings;

[0059] All middlings from the three flotation cycles were sequentially returned. The flotation process was repeated six times. After reaching equilibrium, the quality and grade of the concentrate and tailings obtained in each test remained essentially unchanged. The stabilized concentrate and tailings were sampled and sent for chemical analysis. The results of the closed-circuit flotation tests are shown in Table 1.

[0060] Comparative Example 1

[0061] The process flow and reagent system are basically the same as those in Example 1, except that no serpentine inhibitor is added in the roughing operation and the first cleaning operation. Other reagents are the same as those in Example 1. The closed-circuit test results are shown in Table 1.

[0062] Comparative Example 2

[0063] The process flow and reagent system were the same as those in Example 1, except that conventional sodium hexametaphosphate was used as the serpentine inhibitor, and the amounts of sodium hexametaphosphate and PD were the same. Other conditions remained unchanged. The closed-circuit test results are shown in Table 1.

[0064] Comparative Example 3

[0065] The process flow and reagent system were the same as in Example 1, except that AA / AMPS was used as the serpentine inhibitor, the amounts of AA / AMPS and PD were the same, and other conditions remained unchanged. The closed-circuit test results are shown in Table 1.

[0066] Comparative Example 4

[0067] The process flow and reagent system were the same as those in Example 1, except that DTPMPA was used as the serpentine inhibitor, and the dosages of DTPMPA and PD were the same. Other conditions remained unchanged. The closed-circuit test results are shown in Table 1.

[0068] Comparative Example 5

[0069] The process flow and reagent system were the same as those in Example 1, except that XG was used as the serpentine inhibitor, the dosages of XG and PD were the same, and other conditions remained unchanged. The closed-circuit test results are shown in Table 1.

[0070] Comparative Example 6

[0071] The process flow and reagent system were the same as those in Example 1, except that a combination of AA / AMPS and DTPMPA was used as the serpentine inhibitor. The dosage of the combined inhibitor and PD was the same, and all other conditions remained unchanged. The closed-circuit test results are shown in Table 1.

[0072] AA / AMPS and DTPMPA are composed in a mass ratio of 50:50.

[0073] Comparative Example 7

[0074] The process flow and reagent system were the same as those in Example 1, except that a combination of AA / AMPS and XG was used as the serpentine inhibitor. The dosage of the combined inhibitor and PD was the same, and other conditions remained unchanged. The closed-circuit test results are shown in Table 1.

[0075] AA / AMPS and XG are composed in a mass ratio of 80:20.

[0076] Comparative Example 8

[0077] The process flow and reagent system were the same as those in Example 1, except that a combination of DTPMPA and XG was used as the serpentine inhibitor. The dosage of the combined inhibitor and PD was the same, and other conditions remained unchanged. The closed-circuit test results are shown in Table 1.

[0078] DTPMPA and XG are composed in a mass ratio of 80:20.

[0079] Comparative Example 9

[0080] The process flow and reagent system are the same as those in Example 1, except that the coarse concentrate is not ground and other conditions remain unchanged. The closed circuit test results are shown in Table 1.

[0081] Comparative Example 10

[0082] The raw ore in this comparative example is the same as that in Example 1, and the separation adopts the on-site process flow of "raw ore coarse grinding - tailings regrinding and re-separation". The dosage of all reagents in this comparative example is the addition amount relative to the raw ore. The specific process steps are:

[0083] 1) Crushing and grinding the raw ore to a grinding fineness of -0.074 mm accounting for 65% to obtain ore pulp;

[0084] 2) First stage roughing: add 150g / t of ethyl xanthate to the ore pulp after grinding, stir for 2 minutes, then add 40g / t of butyl ammonium nitrosulfate, stir for 2 minutes, then add 6g / t of 2# oil, stir for 1 minute, aerate flotation, scrape and foam for 3 minutes to obtain the first stage roughing concentrate and the first stage roughing tailings;

[0085] First stage roughing 2: add 60g / t of ethyl xanthate to the first stage roughing tailings, stir for 2 minutes, then add 6g / t of 2# oil, stir for 1 minute, aerate and flotate, and scrape for 2 minutes to obtain the first stage roughing 2 concentrate and the first stage roughing 2 tailings;

[0086] 3) Two selections of one paragraph:

[0087] First stage concentrator 1: Combine the first stage rougher concentrate and the second stage rougher concentrate to perform blank concentrator, aeration flotation, and scraping for 2 minutes to obtain the first stage concentrator concentrate and the first stage concentrator middling 1;

[0088] Stage 2: The first stage concentrate is subjected to blank selection, aeration flotation, and scraping for 2 minutes to obtain copper-nickel concentrate 1 and first stage concentrated middlings 2 (return to the first stage concentration operation);

[0089] 4) Regrinding: The first roughing tailings, the first concentrating middlings 1, the second concentrating middlings 1 and the second scavenging concentrate 1 are combined for regrinding, and the regrinding fineness is -0.038mm, accounting for 81%;

[0090] 5) Secondary roughing: The ore pulp after regrinding is subjected to secondary roughing, and 80 g / t of ethyl xanthate is added and stirred for 2 minutes. 6 g / t of 2# oil is added and stirred for 1 minute. Aeration flotation is performed and the foam is scraped for 2.5 minutes to obtain secondary roughing concentrate and secondary roughing tailings;

[0091] 6) Two-stage sweep selection:

[0092] Second stage scavenging and separation 1: add 30g / t of ethyl xanthate to the second stage roughing tailings, stir for 2 minutes, aerate and float, and scrape for 1.5 minutes to obtain second stage scavenging and separation concentrate 1 (return to the second stage roughing operation) and second stage scavenging and separation tailings 1;

[0093] Second stage scavenging and separation 2: add 10g / t of ethyl xanthate to the tailings of the second stage scavenging and separation 1, stir for 2 minutes, aerate and float, scrape and flot for 1 minute to obtain the second stage scavenging and separation concentrate 2 (return to the second stage scavenging and separation 1 operation) and tailings;

[0094] 7) Three times two-stage selection:

[0095] Secondary concentration 1: The secondary roughing concentrate is subjected to blank concentration, aeration flotation, and scraping for 2 minutes to obtain secondary concentration concentrate 1 and secondary concentration middling 1 (sent to the secondary roughing operation); Secondary concentration 2: The secondary concentration concentrate 1 is subjected to blank concentration, aeration flotation, and scraping for 2 minutes to obtain secondary concentration concentrate 2 and secondary concentration middling 2 (returned to the secondary concentration 1 operation); Secondary concentration 3: The secondary concentration concentrate 2 is subjected to blank concentration, aeration flotation, and scraping for 1.5 minutes to obtain copper-nickel concentrate 2 and secondary concentration middling 3 (returned to the secondary concentration 2 operation);

[0096] The closed-circuit test results are shown in Table 1.

[0097] Comparative Example 11

[0098] This comparative example is basically the same as comparative example 10, except that serpentine inhibitor PD is added in the first roughing operation and the second roughing operation respectively, and other conditions remain unchanged. The details are as follows:

[0099] First stage roughing: add 400g / t of PD, stir for 2 minutes, then add ethyl xanthate and butyl ammonium black powder in sequence; second stage roughing: add 150g / t of PD, stir for 2 minutes, then add ethyl xanthate and 2# oil in sequence.

[0100] The closed-circuit test results are shown in Table 1.

[0101] Table 1 Closed circuit test results of Example 1 and Comparative Examples 1 to 11 / %

[0102]

[0103]

[0104] It can be seen from Table 1 that: ① Under the on-site process flow (Comparative Example 10), without adding serpentine inhibitor, the copper-nickel concentrate 1 has a Cu grade of 2.17%, a Ni grade of 6.70%, a MgO grade of 14.32%, a Cu recovery rate of 59.41%, and a Ni recovery rate of 56.59%; the copper-nickel concentrate 2 has a Cu grade of 1.09%, a Ni grade of 4.82%, and a MgO grade of 13.17%; the Cu recovery rate is 12.48%, and the Ni recovery rate is 17.02%; the combined copper-nickel concentrate has a Cu grade of 1.85%, a Ni grade of 6.15%, a MgO grade of 13.98%, a Cu recovery rate of 71.89%, and a Ni recovery rate of 73.62%. Under on-site process conditions (Comparative Example 11), with the addition of serpentine inhibitor PD, the combined copper-nickel concentrate of copper-nickel concentrates 1 and 2 had a Cu grade of 2.07%, a Ni grade of 7.35%, and a MgO grade of 10.62%. Cu recovery rates were 71.32%, and Ni recovery rates were 73.79%. Combining Comparative Examples 10 and 11, it can be seen that using the on-site "coarse grinding of raw ore - regrinding and reselection of tailings" process flow, regardless of whether the serpentine inhibitor PD was added, the MgO content in the combined copper-nickel concentrate obtained was >10%, the copper recovery rate was approximately 71%, and the nickel recovery rate was approximately 73%. Clearly, the MgO content in the copper-nickel concentrate exceeded the standard. ② Using the novel shortened separation process proposed in the present invention, with the simultaneous addition of the serpentine combined inhibitor PD (Example 1), a copper-nickel concentrate with a Cu grade of 2.79%, a Ni grade of 9.61%, a MgO grade of 5.86%, a Cu recovery rate of 70.81%, and a Ni recovery rate of 72.92% was obtained. Similarly, the novel shortened separation process proposed in the present invention was used, with the addition of sodium hexametaphosphate, a conventional serpentine inhibitor (Comparative Example 2), or one of the three PD components, AA / AMPS (Comparative Example 3), DTPMPA (Comparative Example 4), or XG (Comparative Example 5). Because serpentine enters the copper-nickel concentrate through heterogeneous agglomeration and mechanical entrainment, the MgO content in the copper-nickel concentrate obtained in Comparative Examples 2-4 was >7%. Due to the poor selectivity of xanthan gum alone, although the MgO grade in the copper-nickel concentrate obtained in Comparative Example 5 was 6.25%, the copper and nickel recoveries in the copper-nickel concentrate were both approximately 35%. Similarly, using the novel shortened separation process proposed in the present invention, with the addition of a combination of two of the PD inhibitor components (Comparative Examples 6-8), serpentine also severely interfered with the flotation of the copper-nickel sulfide ore, resulting in a MgO content >6.5% in the copper-nickel concentrate, a copper recovery of 57.11% to 71.60%, and a nickel recovery of 55.10% to 73.32%.④ The new short-process separation process proposed by the present invention is adopted, and PD is added at the same time, but the roughing concentrate is no longer ground, and the copper-nickel concentrate is obtained with a Cu grade of 2.72%, a Ni grade of 9.35%, a MgO grade of 7.35%, a Cu recovery rate of 71.19%, and a Ni recovery rate of 73.16%. Compared with Example 1, no further grinding is performed, the copper recovery rate is increased by 0.38%, the nickel recovery rate is increased by 0.24%, but the MgO content is increased by 1.49%, indicating that regrinding is beneficial to the better dissociation of the aggregates of pentlandite and chalcopyrite from serpentine gangue, etc., and is more conducive to the selective inhibition of serpentine by PD, thereby improving the grade of the copper-nickel concentrate. ⑤ By comparing Example 1 with Comparative Examples 10 and 11, it can be seen that after the tailings are regrinded, the copper recovery rates in Comparative Examples 10 and 11 are increased by 1.08 percentage points and 0.51 percentage points, respectively, and the nickel recovery rates are increased by 0.70 percentage points and 0.09 percentage points, respectively, but the MgO content in the concentrate is increased by 8.12 percentage points and 4.76 percentage points. It shows that for this type of ore, it only needs to be ground until the useful mineral aggregates are dissociated, and there is no need to carry out coarse grinding of the original ore and regrinding and reselection of the tailings. Through the introduction of a new process, combined with the high-efficiency inhibitor PD, while ensuring the recovery rate of copper and nickel, the selective reduction of magnesium in the concentrate is effectively achieved, and the MgO content in the concentrate is less than 6%, which meets the standard.

[0105] Example 2

[0106] A high-serpentine-talc nickel sulfide ore was obtained from Xinjiang. The ore contained valuable elements including Cu and Ni, with a Cu grade of 0.20%, a Ni grade of 0.65%, a SiO2 grade of 26.91%, an Al2O3 grade of 12.90%, a CaO grade of 4.50%, and a MgO grade of 16.34%. The main target minerals in the ore were pentlandite and chalcopyrite, while the main gangue minerals were serpentine, talc, mica, and chlorite. The large amount of easily argillized serpentine, talc, chlorite, and mica in the ore interfered with the flotation of copper and nickel minerals. Furthermore, the flotation rate of the pentlandite in the ore was slow, making it a complex serpentine-bearing copper-nickel sulfide ore.

[0107] The raw ore sample is first crushed and ground to -0.074mm, accounting for 76%. Then the ground ore pulp is poured into the flotation tank for flotation test. The test process and reagent system are as follows: Figure 4 As shown. In this embodiment, all the reagent addition amounts are relative to the original ore. The specific steps are as follows:

[0108] In this embodiment, PD is composed of AA / AMPS, DTPMPA, and XG in a mass ratio of 45:30:25. Before adding PD to the ore slurry, AA / AMPS, DTPMPA, and XG are prepared into aqueous solutions with mass concentrations of 2% AA / AMPS, 2% DTPMPA, and 0.5% XG, respectively. The three aqueous solutions are then added to the ore slurry.

[0109] In this embodiment, the process adopts two roughing, three sweeping and two fine grinding, and the coarse concentrate is re-grinded.

[0110] 1) Secondary roughing

[0111] Roughing 1: add 300g / t of PD to the ground slurry, stir for 2 minutes, add 120g / t of ethyl xanthate, stir for 2 minutes, add 30g / t of butyl ammonium black powder, stir for 2 minutes, aerate and flotate, and scrape for 3 minutes to obtain copper-nickel roughing 1 concentrate and roughing 1 tailings.

[0112] Roughing II: add 50g / t of PD to the roughing II tailings, stir for 2 minutes, add 70g / t of ethyl xanthate, stir for 2 minutes, add 20g / t of butyl ammonium black powder, stir for 2 minutes, aerate and flotate, and scrape for 2 minutes to obtain the copper-nickel roughing II concentrate and roughing II tailings.

[0113] 2) Regrinding: The copper-nickel coarse primary concentrate and the copper-nickel coarse secondary concentrate are combined into a copper-nickel coarse concentrate, and then subjected to ball milling and regrinding. The grinding fineness is -0.038mm, accounting for 82%.

[0114] 3) Three scans

[0115] Scavenging 1: Add 40g / t of ethyl xanthate to the roughing 2 tailings, stir for 2 minutes, add 10g / t of butyl ammonium nitrate, stir for 2 minutes, aerate and flotate, and scrape for 1.5 minutes to obtain scavenging 1 concentrate (return to the roughing 1 operation) and scavenging 1 tailings;

[0116] Scavenging 2: Add 30g / t of ethyl xanthate to the tailings of scavenging 1, stir for 2 minutes, aerate and float, scrape and foam for 1 minute to obtain scavenging 2 concentrate (return to scavenging 1 operation) and scavenging 2 tailings;

[0117] Scavenging and separation 3: add 15g / t of ethyl xanthate to the tailings of scavenging and separation 2, stir for 2 minutes, aerate and float, scrape and flot for 1 minute to obtain scavenging and separation 3 concentrate (return to scavenging and separation 2 operation) and tailings;

[0118] 4) Two selections

[0119] Concentrator 1: Add PD 100g / t to the regrinded copper-nickel rough concentrate, stir for 2 minutes, aerate and flotate, and scrape for 2 minutes to obtain concentrate 1 (return to rougher 1 operation) and concentrate 1 middlings;

[0120] Concentration 2: blank concentration is performed on the concentrate 1, aeration flotation is performed, and foaming is performed for 2 minutes to obtain the concentrate and the concentrate 2 middlings (returned to the concentration 1 operation);

[0121] All middlings from the three flotation cycles were sequentially returned. The flotation process was repeated six times. After reaching equilibrium, the quality and grade of the concentrate and tailings obtained in each test remained essentially unchanged. The stabilized concentrate and tailings were sampled and sent for chemical analysis. The results of the closed-circuit flotation test are shown in Table 2.

[0122] Comparative Example 12

[0123] The process flow and reagent system were basically the same as those in Example 2, except that the amount of serpentine inhibitor PD added in the roughing operation was 100 g / t, and other conditions remained unchanged. The closed-circuit test results are shown in Table 2.

[0124] Example 3

[0125] The process flow and reagent system were basically the same as those in Example 2, except that the amount of serpentine inhibitor PD added in the roughing operation was 500 g / t, and other conditions remained unchanged. The closed-circuit test results are shown in Table 2.

[0126] Comparative Example 13

[0127] The process flow and reagent system were basically the same as those in Example 2, except that the amount of serpentine inhibitor PD added in the roughing operation was 800 g / t, and other conditions remained unchanged. The closed-circuit test results are shown in Table 2.

[0128] Comparative Example 14

[0129] The raw ore of this comparative example is the same as that of Example 2, and the separation adopts the on-site desludging flotation process. The dosage of all reagents in this comparative example is the addition amount relative to the raw ore. The specific process steps are:

[0130] 1) Crushing and grinding the raw ore, with a grinding fineness of -0.074mm accounting for 76%, to obtain ore pulp;

[0131] 2) Desludging and sweeping

[0132] Roughing: Add 21g / t pine oil to the ore pulp after grinding, stir for 1 minute, and scrape for 2 minutes to obtain deslimed concentrate 1 and deslimed roughing tailings;

[0133] Scavenging: add 7g / t pine oil to the deslimed roughing tailings, stir for 1 minute, and scrape for 1.5 minutes to obtain deslimed concentrate 2 and deslimed scavenging tailings; deslimed concentrate 1 and deslimed concentrate 2 are combined to form deslimed concentrate.

[0134] 3) Secondary roughing:

[0135] Roughing 1: add 300g / t of sodium hexametaphosphate to the desludging and sweeping tailings, stir for 2 minutes, add 120g / t of ethyl xanthate, stir for 2 minutes, add 30g / t of butyl ammonium black powder, stir for 2 minutes, aerate and flotate, and scrape for 3 minutes to obtain copper-nickel roughing 1 concentrate and roughing 1 tailings.

[0136] Roughing II: add 50g / t of sodium hexametaphosphate to the roughing II tailings, stir for 2 minutes, add 70g / t of ethyl xanthate, stir for 2 minutes, add 20g / t of butyl ammonium black powder, stir for 2 minutes, aerate and float, scrape and foam for 2 minutes to obtain the copper-nickel roughing II concentrate and roughing II tailings.

[0137] 4) Three scans

[0138] Scavenging 1: Add 40g / t of ethyl xanthate to the roughing 2 tailings, stir for 2 minutes, add 10g / t of butyl ammonium nitrate, stir for 2 minutes, aerate and flotate, and scrape for 1.5 minutes to obtain scavenging 1 concentrate (return to the roughing 1 operation) and scavenging 1 tailings;

[0139] Scavenging 2: Add 30g / t of ethyl xanthate to the tailings of scavenging 1, stir for 2 minutes, aerate and float, scrape and foam for 1 minute to obtain scavenging 2 concentrate (return to scavenging 1 operation) and scavenging 2 tailings;

[0140] Scavenging and separation 3: add 15g / t of ethyl xanthate to the tailings of scavenging and separation 2, stir for 2 minutes, aerate and float, scrape and flot for 1 minute to obtain scavenging and separation 3 concentrate (return to scavenging and separation 2 operation) and tailings;

[0141] 5) Two selections

[0142] Concentration 1: Combine the copper-nickel rougher concentrate 1 and the copper-nickel rougher concentrate 2 to form a copper-nickel rougher concentrate, add 120g / t of sodium hexametaphosphate, stir for 2 minutes, aerate and flotate, and scrape for 2 minutes to obtain concentrate 1 and middling 1 (return to rougher 1 operation);

[0143] Concentration 2: Blank selection is performed on the concentrate of Concentration 1, aeration flotation is performed, and foaming is performed for 2 minutes to obtain concentrate and Concentration 2 middlings (return to Concentration 1 operation).

[0144] The flotation process was repeated six times. After reaching equilibrium, the quality and grade of the concentrate and tailings obtained in each test remained essentially constant. Samples of the stabilized concentrate and tailings were taken for chemical analysis. The results of the closed-circuit flotation tests are shown in Table 2.

[0145] Table 2 Closed circuit test results of Examples 2-3 and Comparative Examples 12-14 / %

[0146]

[0147] It can be seen from Table 2 that: ① Under the on-site process flow and reagent system (Comparative Example 14), pre-desliming can reduce the interference of muddy gangue on copper-nickel flotation, but will cause the loss of nickel and copper. The loss rates of copper and nickel in the deslimed concentrate are 7.06% and 6.95%, respectively. The copper-nickel concentrate has a Cu grade of 2.47%, a Ni grade of 8.01%, and a MgO grade of 7.49%. The Cu recovery rate is 67.40%, and the Ni recovery rate is 70.61%. ② By adopting the new separation process proposed by the present invention and adding 300 g / tPD of serpentine inhibitor at the same time (Example 2), the copper-nickel concentrate has a Cu grade of 2.44%, a Ni grade of 7.98%, a MgO grade of 5.24%, a Cu recovery rate of 73.90%, and a Ni recovery rate of 75.75%. Compared with Example 2, the PD dosage was reduced to 100 g / t (Comparative Example 12), and the Cu grade in the copper-nickel concentrate was reduced by 0.39 percentage points, the Ni grade was reduced by 1.78 percentage points, the MgO grade was 7.97%, and the Cu recovery rate and the nickel recovery rate increased slightly, increasing by 0.37 percentage points, and the Ni recovery rate was 0.27 percentage points respectively. Compared with Example 2, the PD dosage was increased to 500 g / t (Example 3), and the Cu grade in the copper-nickel concentrate was 2.52%, the Ni grade was 8.49%, and the MgO grade was 5.21%. , Cu recovery rate is 73.58%, Ni recovery rate is 75.12%, copper-nickel indicators do not change much, and the MgO grade in the copper-nickel concentrate remains basically unchanged; the PD dosage is continued to increase to 800 g / t (Comparative Example 13), and the Cu grade in the copper-nickel concentrate is 2.87%, the Ni grade is 8.95%, and the MgO grade is 5.18%. However, the Cu recovery rate is only 65.58%, and the Ni recovery rate is only 61.05%. Obviously, excessive PD dosage not only fails to continue to reduce the MgO content in the copper-nickel concentrate, but also reduces the copper and nickel recovery rates.

[0148] In summary, a rational process flow and reagent system are crucial for improving the performance of copper-nickel concentrates when selecting this type of ore. A shortened separation process, "raw ore grinding - coarse concentrate regrinding and reselection," is employed. After grinding the ore until the pentlandite aggregates are substantially dissociated from the gangue minerals, the gangue tailings are discarded, and the coarse concentrate is regrinded and reselected. Combined with the use of a gangue depressant (PD), which is highly selective for argillaceous gangues such as serpentine, this effectively reduces the MgO content in the copper-nickel concentrate. This process avoids the problems inherent in the complex "raw ore grinding - tailings regrinding and reselection" process, which can lead to increased muddiness of serpentine and other gangue, resulting in continuous circulation and difficulty in suppressing them in the flotation system. It also avoids the problem of pre-desilting and the resulting loss of valuable metals. The use of a highly effective PD depressant reduces the amount of ore circulating throughout the flotation system, resulting in clear foam and a smooth, easy-to-operate process. This process is therefore readily industrially feasible.

Claims

1. A serpentine inhibitor PD, characterized in that The serpentine inhibitor PD is composed of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, diethylenetriamine penta (methylene phosphonic acid) and xanthan gum, wherein the mass ratio of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, diethylenetriamine penta (methylene phosphonic acid) and xanthan gum is (60-30): (40-20): (25-10).

2. The serpentine inhibitor PD according to claim 1, characterized in that The acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer is prepared by copolymerization of acrylic acid and 2-methylpropanesulfonic acid.

3. Use of the serpentine depressant PD according to any one of claims 1 to 2 in the flotation of high-serpentine nickel sulfide ores.

4. A method for efficiently separating high-serpentine nickel sulfide ore, comprising the following steps: 1) Ore grinding: After the ore is crushed, it is wet-milled to obtain flotation slurry; 2) Roughing: transferring the flotation pulp into a flotation tank, adding the serpentine inhibitor PD, ethyl xanthate, and butyl ammonium nitrosulfate as claimed in claim 1 or 2 to the pulp, and performing roughing operation to obtain nickel roughing concentrate and roughing tailings respectively; 3) Regrinding the rougher concentrate: Regrinding the nickel rougher concentrate to obtain a reground rougher concentrate slurry; 4) Concentration: Add the serpentine inhibitor PD to the regrinded rougher concentrate slurry to perform concentrating operations to obtain concentrate and middlings; the middlings are returned to the previous flotation operation; 5) Scavenging: Add ethyl xanthate and butyl ammonium nitrosulfate to the roughing tailings for scavenging to obtain scavenging concentrate and tailings; the scavenging concentrate is returned to the previous flotation operation.

5. The method according to claim 4, characterized in that In step 1), the raw ore is crushed and then wet ball milled, with a grinding fineness of -0.074 mm accounting for 75-85%, so that the pentlandite aggregate and the gangue minerals are fully dissociated to obtain the flotation slurry.

6. The method according to claim 4, characterized in that In step 2), the roughing operation is one to two roughing operations: When the roughing operation is a single roughing operation, the specific process flow is as follows: first add PD 200-700g / t, stir for 2-3 minutes; then add ethyl xanthate 50-300g / t, stir for 2-3 minutes; then add butyl ammonium black powder 20-100g / t, stir for 2-3 minutes, perform roughing operation, scrape and foam for 2-5 minutes, and obtain nickel roughing concentrate and roughing tailings respectively; When the roughing operation is secondary roughing, the specific steps are: Roughing 1: first add PD 200-700g / t, stir for 2-3 minutes; then add ethyl xanthate 50-300g / t, stir for 2-3 minutes; then add butyl ammonium nitrosulfate 20-100g / t, stir for 2-3 minutes, and then carry out roughing 1 operation. Scrape and foam for 2-5 minutes to obtain nickel roughing 1 concentrate and roughing 1 tailings respectively; Roughing II: first add 50-200g / t of PD to the roughing I tailings and stir for 2-3 minutes; then add 25-150g / t of ethyl xanthate and stir for 2-3 minutes; then add 10-50g / t of butyl ammonium black powder and stir for 2-3 minutes, and carry out the roughing II operation. Scrape and foam for 2-5 minutes to obtain nickel roughing II concentrate and roughing II tailings respectively; the nickel roughing I concentrate and nickel roughing II concentrate are combined into nickel roughing concentrate.

7. The method according to claim 4, characterized in that In step 3), the nickel rougher concentrate is ground again to a fineness of -0.038 mm, accounting for 70-85%.

8. The method according to claim 4, characterized in that In step 4), the selection process is performed twice, specifically: Copper Concentration 1: Add 100-300g / t of PD to the regrinding rougher concentrate slurry and stir for 2-3 minutes to carry out copper concentration 1 to obtain copper concentration 1 concentrate and copper concentration middlings 1; copper concentration middlings 1 are returned to the rougher concentration 1; Concentration 2: Blank concentration is performed on the copper concentrate 1 to obtain nickel concentrate and nickel concentrate middlings 2; the nickel concentrate middlings 2 are returned to the concentration 1 operation.

9. The method according to claim 4, characterized in that In step 5), the scanning operation is three times, specifically: Scavenging 1: Add 25-150g / t of ethyl xanthate to the roughing tailings, stir for 2-3 minutes, add 10-50g / t of butyl ammonium nitrosulfate, stir for 2-3 minutes, carry out scavenging 1, scrape and foam for 1-3 minutes to obtain nickel scavenging 1 concentrate and nickel scavenging 1 tailings respectively; the nickel scavenging 1 concentrate is returned to the roughing 1 operation; Scavenging 2: Add 13-75g / t of ethyl xanthate to the nickel scavenging 1 tailings, stir for 2-3 minutes, add 10-50g / t of butyl ammonium black powder, stir for 2-3 minutes, carry out scavenging 2 operation, scrape and foam for 1-3 minutes to obtain nickel scavenging 2 concentrate and nickel scavenging 2 tailings respectively; the nickel scavenging 2 concentrate is returned to the scavenging 1 operation; Scavenging and selection three: add 10-40g / t of ethyl xanthate to the nickel scavenging and selection two tailings, stir for 2-3 minutes, carry out scavenging and selection three operation, scrape and foam for 1-3 minutes, and obtain nickel scavenging and selection three concentrate and tailings respectively; the nickel scavenging and selection three concentrate is returned to the scavenging and selection two operation.

10. The method according to claim 4, characterized in that The serpentine inhibitor PD is added by first preparing acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer, diethylenetriamine penta (methylene phosphonic acid) and xanthan gum into aqueous solutions, wherein the mass concentration of acrylic acid-2-acrylamide-2-methylpropanesulfonic acid copolymer is 1-5%, the mass concentration of diethylenetriamine penta (methylene phosphonic acid) is 1-5%, and the mass concentration of xanthan gum is 0.5-1%, and then adding the aqueous solutions together into the ore pulp.

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