A combined direct and reverse flotation method for reducing lead content of copper concentrate

Abstract

The application discloses a positive and reverse flotation combined beneficiation method for reducing the lead content of copper concentrate. First, copper-lead mixed flotation is carried out on raw ore to realize synchronous enrichment of copper and lead valuable minerals. Then, copper-lead mixed concentrate is subjected to copper-inhibiting lead-flotation positive flotation to preferentially float out lead concentrate and separate to obtain coarse copper concentrate. Finally, copper-inhibiting lead-flotation reverse flotation is carried out to deeply remove lead minerals entrained in the copper concentrate, and low-lead qualified copper concentrate is obtained. The tailings of the whole reverse flotation process are uniformly returned to the front end of the copper-inhibiting lead-flotation roughing operation to build a closed loop system. Industrial application shows that the process can efficiently strip lead inclusions in the copper concentrate, is suitable for various types of refractory copper-lead associated ores, can stably reduce the lead content of copper concentrate exceeding the standard to the qualified range of the national standard, guarantees the overall recovery rate of copper and lead metals, the process flow is simple, the on-site reconstruction difficulty is low, and the process is suitable for large-scale industrial application of mines.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal sulfide ore beneficiation technology, and relates to a flotation separation process for copper-lead symbiotic sulfide ores, and particularly to a combined flotation method specifically designed to solve the problem of excessive lead content in copper concentrate. Background Technology

[0002] Copper-lead symbiotic sulfide ores are important sources of copper and lead metals in my country. Chalcopyrite and galena in these ores have very similar natural floatability and contain a large number of copper-lead intergrowths and fine-grained inclusions, making them typical difficult-to-separate ores in the beneficiation field. Currently, the mainstream beneficiation processes in mines include two main categories: preferential flotation and mixed flotation. In preferential flotation, copper is floated first and then lead, making it very easy for lead minerals to be carried into the copper concentrate, resulting in high levels of lead impurities in the copper concentrate. Traditional mixed flotation, relying on only one separation, cannot completely separate fine-grained lead intergrowths, and the preceding flotation reagents continue to be adsorbed on the mineral surface, significantly reducing the selectivity of subsequent separations. Ultimately, this results in the copper concentrate having excessive lead content, failing to meet copper concentrate quality standards.

[0003] Specifically, the existing process has three major flaws: First, it only uses single-stage unidirectional flotation without a combination of forward and reverse flotation for deep purification, making it difficult to remove fine lead inclusions; second, it lacks a targeted de-removal process, as residual reagents from the previous flotation stage passivate the mineral surface, resulting in extremely poor separation efficiency when directly performing secondary flotation; and third, it lacks a reasonable closed-loop tailings recirculation design, leading to a large loss of fine copper metal from the tailings. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a combined forward and reverse flotation beneficiation method for reducing the lead content in copper concentrate, thereby solving the problems of poor copper-lead separation selectivity, interference from residual reagents in the preceding process, severe lead inclusions in copper concentrate, and low metal recovery rate in the existing copper-lead flotation process.

[0005] The technical solution of the present invention is as follows: A combined forward and reverse flotation beneficiation method for reducing lead content in copper concentrate, comprising the following steps in sequence: Step 1: Grind the raw ore and adjust the pulp, add pH adjuster, gangue inhibitor, copper-lead common collector and frother, and carry out copper-lead mixed roughing; the copper-lead mixed roughing concentrate is then subjected to primary and secondary cleaning to obtain copper-lead mixed concentrate; the roughing tailings are subjected to primary, secondary and tertiary scavenging, and the scavenging concentrate is returned to the previous stage of flotation operation step by step, and the final mixed flotation tailings are either used in the zinc beneficiation process or discharged. Step 2: The copper-lead mixed concentrate produced in Step 1 is slurry prepared by adding copper mineral inhibitor, lead selective collector and frother, and copper-suppressed lead-floted roughing flotation is carried out. The floating product is lead rough concentrate, which is then processed through a first stage and a second stage of cleaning to obtain lead concentrate. The roughing underflow is processed through a first stage, a second stage and a third stage of scavenging. The scavenged concentrate is returned to the previous stage of flotation operation step by step, and the scavenging tailings are used as de-reagent feed. Step 3: The crude copper concentrate produced in Step 2 is fed into a mixing tank, and activated carbon is added for forced stirring and de-drug removal. Step 4: Adjust the crude copper concentrate from Step 3 by adding lead mineral inhibitor, copper selective collector and frother, and carry out lead-suppressed and copper-floted reverse flotation roughing. The floating product is then treated by a first-stage and a second-stage cleaning process to obtain low-lead qualified copper concentrate. The roughing tailings are then treated by a first-stage, a second-stage, and a third-stage scavenging process. The concentrates from each stage of scavenging are returned to the next stage of flotation operation. Finally, all the tailings from the reverse flotation are returned to the front end of the copper-suppressed and lead-floted forward flotation roughing operation in Step 2, forming a closed loop.

[0006] Preferably, in step one, the pH adjuster for the copper-lead mixed roughing is lime, with a dosage of 1000-1200 g / t; the gangue inhibitor is sodium sulfite, with a dosage of 600-800 g / t; the copper-lead shared collector is ethyl thiocyanate, with a dosage of 30-50 g / t; and the foaming agent is No. 2 oil, with a dosage of 15-25 g / t. In the first stage of refining, the dosages are: lime 200-300 g / t, sodium sulfite 150-200 g / t, and No. 2 oil 3-6 g / t; in the second stage of refining, the dosage of No. 2 oil is 1-3 g / t; and the dosages of ethyl thiocyanate in the first, second, and third stages of refining are 5-10 g / t, 3-6 g / t, and 1-4 g / t, respectively, and the dosages of No. 2 oil are 2-4 g / t, 1-3 g / t, and 1-2 g / t, respectively.

[0007] Preferably, in step two, the pH adjuster for the roughing flotation is sodium carbonate, with a dosage of 500–600 g / t; the copper mineral depressant is sodium thioglycolate and sodium sulfide, with dosages of 300–400 g / t and 700–900 g / t, respectively; the lead selective collector is butyl xanthate, with a dosage of 35–50 g / t; and the frother is No. 2 oil, with a dosage of 12–20 g / t. In the first stage of the cleaning process, the dosages are: sodium carbonate 150–200 g / t, sodium thioglycolate 15 g / t. 0-200 g / t, No. 2 oil 3-6 g / t; second-stage refined sodium thioglycolate 80-100 g / t, No. 2 oil 1-3 g / t; first-stage, second-stage, and third-stage scavenging sodium sulfide dosages are 150-200 g / t, 80-120 g / t, and 40-60 g / t respectively, butyl xanthate dosages are 8-12 g / t, 4-8 g / t, and 2-5 g / t respectively, and No. 2 oil dosages are 2-4 g / t, 1-3 g / t, and 1-2 g / t respectively.

[0008] Preferably, in step three, based on the dry weight of crude copper concentrate, the amount of activated carbon added is 1000-1400 g / t, the stirring speed is 200-250 r / min, the stirring time is 8-12 min, and the slurry concentration in the de-chemical process is 25%-30%.

[0009] Preferably, in step four, the reverse flotation roughing pH adjuster is lime, with a dosage of 600-800 g / t; the lead mineral depressant is sodium humate and sodium thiosulfate, with dosages of 1000-1200 g / t and 500-600 g / t, respectively; the copper selective collector is ethyl thiocyanate Z-200, with a dosage of 25-35 g / t; and the frother is No. 2 oil, with a dosage of 12-18 g / t. The first stage of the cleaning process uses 200-250 g / t of lime and sodium humate. 350-400g / t, No. 2 oil 3-5g / t; second-stage refined sodium humate 150-200g / t, No. 2 oil 1-3g / t; first-stage, second-stage, and third-stage scavenging sodium thiosulfate dosages are 120-150g / t, 70-90g / t, and 30-50g / t respectively, Z-200 dosages are 5-8g / t, 3-5g / t, and 1-3g / t respectively, and No. 2 oil dosages are 2-4g / t, 1-3g / t, and 1-2g / t respectively.

[0010] Compared with the prior art, the present invention has the following beneficial effects.

[0011] First, this invention first removes most of the lead minerals in advance through copper-suppressing and lead-flotation direct flotation, and then further removes fine lead inclusions through lead-suppressing and copper-flotation reverse flotation. This two-stage separation completely solves the problem of excessive lead in copper concentrate. Examples of this invention show that the lead content in copper concentrate can be reduced from 7.23% to 2.26% (medium-sized disseminated ore) or from 8.95% to 2.85% (high-fine-grained, difficult-to-process ore), with a reduction exceeding 68%, consistently meeting the national Class I standard; furthermore, copper and lead recovery rates are improved to a certain extent, and the process operates stably.

[0012] Secondly, by adding an activated carbon de-doping process, this invention specifically addresses the problem of interference from residual flotation reagents in the preceding flotation process, avoids separation failure caused by reagent film on the mineral surface, and significantly improves the separation accuracy of copper-lead in reverse flotation.

[0013] Third, the three-stage flotation process of this invention adopts a closed-circuit process of roughing, cleaning and scavenging, which has a higher degree of standardization of the whole process and is more convenient for on-site equipment matching and production operation in mines.

[0014] Fourth, in this invention, all tailings from reverse flotation are returned to the front end of the lead-suppressing and copper-floating roughing operation for further recovery of fine-grained copper metal, which can better ensure the copper metal recovery rate.

[0015] Fifth, this invention completely eliminates highly toxic mineral processing reagents such as cyanide and dichromate, and adopts environmentally friendly combined inhibitors and selective collectors, with no highly toxic mineral processing reagents; industrial implementation does not require large-scale modification of the original flotation production line, only the addition of a simple de-reagent stirring tank, and the threshold for industrialization is low. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of an embodiment of the combined mineral processing method of the present invention. Detailed Implementation

[0017] The present invention will be further illustrated below with reference to embodiments and experimental data.

[0018] The pulp concentrations used in this invention are: 33%-36% for mixed flotation, 29%-31% for direct and reverse flotation, and 30% for the dewatering process.

[0019] The No. 2 oil used in this invention is pine oil, and Z-200 is ethyl thiocyanate. Example 1

[0020] A medium-sized copper-lead sulfide ore with disseminated grains from Southwest China was selected as the test raw material. The original ore had a copper grade of 1.82% and a lead grade of 4.16%. The existing on-site process used a traditional mixed flotation-single separation process, resulting in long-term excessive lead impurities in the copper concentrate. The process of this invention (see [link to invention]) was then employed. Figure 1 Closed-circuit flotation tests were conducted, and the results were compared with the existing process.

[0021] This embodiment is divided into four core units: mixed copper-lead flotation of raw ore, copper-suppressing and lead-flotating direct flotation, activated carbon deretting, and lead-suppressing and copper-flotating reverse flotation. All flotation units uniformly adopt a closed-circuit mode of one roughing, two cleaning, and three scavenging processes. The specific steps are as follows: Step 1: Copper-lead mixed flotation of raw ore (roughing, cleaning, and scavenging)

[0022] The raw ore is ground to control the grinding fineness, with -0.074mm particles accounting for 83%–89%, and the pulp concentration adjusted to 33%–36%. Lime (1100g / t) is added to adjust the pH to 8.5–9.0. Sodium sulfite (750g / t) (to suppress gangue and sphalerite), ethyl thiocyanate (40g / t) (copper-lead co-collector), and No. 2 oil (20g / t) (foaming agent) are added sequentially, followed by copper-lead mixed roughing for 9 minutes. The roughing concentrate then enters a primary cleaning stage (corresponding to…). Figure 1 (Mixed roughing concentrate, stage I), add 250g / t lime, 180g / t sodium sulfite, and 5g / t No. 2 oil, and refine for 6 minutes; the refined concentrate from stage I enters stage II refinement (corresponding to...) Figure 1 The mixed roughing concentrate (refining II) is processed by adding 2g / t of No. 2 oil and refining for 5 minutes to obtain a copper-lead mixed concentrate; the tailings from the refining are returned step by step. The roughing tailings are sequentially sent to the first scavenger, second scavenger, and third scavenger (corresponding to...). Figure 1 The copper-lead mixed flotation tailings were scavenged in stages I, II, and III. Each scavenging stage was supplemented with ethyl thiocyanate at 8 g / t, 5 g / t, and 2 g / t, and No. 2 oil at 3 g / t, 2 g / t, and 1 g / t, respectively. The scavenging time was 4 minutes for each stage. The scavenged concentrate was returned step by step, and the final mixed flotation tailings were discharged. Step 2: Mixed flotation of concentrate to suppress copper and lead (one roughing, two cleaning, three scavenging, and direct flotation)

[0023] The copper-lead mixed concentrate obtained in step one was slurried to a concentration of 29%–31%. Sodium carbonate (600 g / t) was added to adjust the pH to 10–11. Sodium thioacetate (350 g / t), sodium sulfide (800 g / t, copper mineral assemblage inhibitor), butyl xanthate (42 g / t, lead selective collector), and No. 2 oil (16 g / t) were added for copper suppression and lead flotation roughing for 9 minutes. The floated lead rough concentrate then entered a primary cleaning stage (corresponding to…). Figure 1 (For the first stage of lead concentrate refining), add 180g / t of sodium carbonate, 180g / t of sodium thioglycolate, and 4g / t of No. 2 oil, and refine for 6 minutes; the first stage concentrate then enters the second stage of refining (corresponding to...). Figure 1 (For the lead rough concentrate from the rougher stage, add 90 g / t of sodium thioacetate and 2 g / t of No. 2 oil, and concentrate for 5 minutes to obtain lead concentrate. The rougher underflow is crude copper concentrate, which is then sequentially fed into the first scavenger, second scavenger, and third scavenger stages (corresponding to...). Figure 1 The medium-copper concentrate is scavenged in stages I, II, and III. Sodium sulfide is added at 160g / t, 100g / t, and 50g / t respectively, butyl xanthate at 10g / t, 6g / t, and 3g / t respectively, and No. 2 oil at 3g / t, 2g / t, and 1g / t respectively. The scavenging time is 4 minutes for each stage. The scavenged concentrate is returned step by step, and the scavenging tailings (containing lead and copper concentrate) are used as de-reagent feed to enter step three.

[0024] This step of the positive flotation prioritizes the removal of most lead minerals from the pulp, reducing the amount of lead inclusions in the subsequent copper concentrate from the source. Step 3: Pretreatment of crude copper concentrate with activated carbon for desiccant removal

[0025] The crude copper concentrate (lead-copper concentrate) produced in step two is fed into a mixing tank (slurry concentration 29%~31%), and 1200g / t of activated carbon is added according to the dry ore amount. The mixture is stirred at 220r / min for 10min to remove residual reagents on the mineral surface using the strong adsorption properties of activated carbon. The mixture is then fed into step four for reverse flotation. Step 4: Lead and copper flotation after reagent removal (roughing, cleaning, scavenging, reverse flotation + tailings recirculation)

[0026] After the crude copper concentrate is treated and slurry is prepared, 700 g / t of lime is added to adjust the pH to 10-11. Then, 1100 g / t of sodium humate, 500 g / t of sodium thiosulfate (lead mineral inhibitor), 28 g / t of Z-200 (ethyl thiocyanate) (copper selective collector), and 15 g / t of No. 2 oil are added for lead-suppressing and copper flotation roughing for 9 minutes. The floated product then enters a primary cleaning stage (corresponding to...). Figure 1 (I) Fine treatment of copper rough concentrate: Add 220g / t lime, 380g / t sodium humate, and 4g / t No. 2 oil, and fine treatment for 6 minutes; the first stage concentrate then enters the second stage fine treatment (corresponding to... Figure 1 (For the copper roughing concentrate (II), 180 g / t of sodium humate and 2 g / t of No. 2 oil are added, and the concentrate is refined for 5 minutes to obtain a low-lead qualified copper concentrate. The roughing tailings are then sequentially fed into the first scavenger, second scavenger, and third scavenger processes (corresponding to...). Figure 1 The tailings from the roughing and intermediate flotation are scavenged in stages I, II, and III. Sodium thiosulfate is added at 130 g / t, 80 g / t, and 40 g / t respectively, along with Z-200 (ethyl thiocyanate) at 7 g / t, 4 g / t, and 2 g / t respectively, and No. 2 oil at 3 g / t, 2 g / t, and 1 g / t respectively. The scavenging time is 4 minutes for each stage. The scavenged concentrate is returned step by step. The final tailings from the reverse flotation are all returned to the front end of the copper-suppressing and lead-floating roughing operation in step two, achieving closed-loop recovery. Table 1 compares the industrial test indicators of this embodiment with those of the original process.

[0027] Table 1

[0028] The results show that after the process modification, the lead content in the copper concentrate decreased from 7.23% to 2.26%, with a lead impurity reduction of up to 68.74%. The copper concentrate directly meets the national first-grade copper concentrate standard, eliminating the need for subsequent beneficiation. Simultaneously, the copper content in the lead concentrate decreased, and the copper and lead recovery rates increased by 2.24% and 2.83%, respectively. The activated carbon dewatering process completely eliminated interference from preceding reagents, and the combined forward and reverse flotation achieved two-stage lead reduction. The process operated stably, without the vicious cycle of middlings. The technical modification only required the addition of a dewatering mixing tank, resulting in extremely low equipment modification costs. Example 2

[0029] A certain ore beneficiation plant has a copper grade of 1.46% and a lead grade of 3.78%. The ore has a high proportion of fine particles and a high content of copper-lead intergrowths. Lead minerals are easily mechanically carried into the copper concentrate, making it a difficult-to-reduce copper-lead ore. The problem of excessive lead in the copper concentrate due to the original process is difficult to completely solve.

[0030] The original production process was replaced by the process of this invention (the process and reagent system are basically the same as those in Example 1), and it was run continuously for 45 days. The comparative indicators are shown in Table 2.

[0031] Table 2

[0032] The results show that this process still exhibits strong lead reduction capabilities for refractory ores with high fine-particle content and numerous intergrowths. The lead content in copper concentrate decreased from 8.95% to 2.85%, a reduction of 68.16%. Activated carbon decanting completely solves the separation failure problem caused by reagent adsorption on the surface of fine-particle minerals, and closed-loop reflux of reverse flotation tailings effectively recovers fine-particle copper metal. Compared with traditional processes, this solution achieves dual lead reduction from two dimensions: macroscopic lead mineral removal and microscopic fine-particle lead inclusion removal. It is perfectly suited for highly refractory copper-lead ores and solves the technical challenge of removing fine-particle lead in the industry.

Claims

1. A combined forward and reverse flotation beneficiation method for reducing lead content in copper concentrate, characterized in that... Follow these steps in sequence: Step 1: Grind the raw ore and adjust the pulp, add pH adjuster, gangue inhibitor, copper-lead common collector and frother, and carry out copper-lead mixed roughing; the copper-lead mixed roughing concentrate is then subjected to primary and secondary cleaning to obtain copper-lead mixed concentrate; the roughing tailings are subjected to primary, secondary and tertiary scavenging, and the scavenging concentrate is returned to the previous stage of flotation operation step by step, and the final mixed flotation tailings are either used in the zinc beneficiation process or discharged. Step 2: The copper-lead mixed concentrate produced in Step 1 is slurry prepared by adding copper mineral inhibitor, lead selective collector and frother, and copper-suppressed lead-floted roughing flotation is carried out. The floating product is lead rough concentrate, which is then processed through a first stage and a second stage of cleaning to obtain lead concentrate. The roughing underflow is processed through a first stage, a second stage and a third stage of scavenging. The scavenged concentrate is returned to the previous stage of flotation operation step by step, and the scavenging tailings are used as de-reagent feed. Step 3: The crude copper concentrate produced in Step 2 is fed into a mixing tank, and activated carbon is added for forced stirring and de-drug removal. Step 4: Adjust the crude copper concentrate from Step 3 by adding lead mineral inhibitor, copper selective collector and frother, and carry out lead-suppressed and copper-floted reverse flotation roughing. The floating product is then treated by a first-stage and a second-stage cleaning process to obtain low-lead qualified copper concentrate. The roughing tailings are then treated by a first-stage, a second-stage, and a third-stage scavenging process. The concentrates from each stage of scavenging are returned to the next stage of flotation operation. Finally, all the tailings from the reverse flotation are returned to the front end of the copper-suppressed and lead-floted forward flotation roughing operation in Step 2, forming a closed loop.

2. The combined forward and reverse flotation beneficiation method for reducing lead content in copper concentrate as described in claim 1, characterized in that: In step one, the pH adjuster for the copper-lead mixed roughing is lime, with a dosage of 1000-1200 g / t; the gangue inhibitor is sodium sulfite, with a dosage of 600-800 g / t; the copper-lead shared collector is ethyl thiocyanate, with a dosage of 30-50 g / t; and the frother is No. 2 oil, with a dosage of 15-25 g / t. In the first stage of refining, the dosages are: lime 200-300 g / t, sodium sulfite 150-200 g / t, and No. 2 oil 3-6 g / t; in the second stage of refining, the dosage of No. 2 oil is 1-3 g / t; and the dosages of ethyl thiocyanate for the first, second, and third stages of refining are 5-10 g / t, 3-6 g / t, and 1-4 g / t, respectively, and the dosages of No. 2 oil are 2-4 g / t, 1-3 g / t, and 1-2 g / t, respectively.

3. The combined forward and reverse flotation beneficiation method for reducing lead content in copper concentrate as described in claim 1, characterized in that: In step two, the pH adjuster for the roughing stage of the positive flotation is sodium carbonate, at a dosage of 500–600 g / t; the copper mineral depressants are sodium thioglycolate and sodium sulfide, at dosages of 300–400 g / t and 700–900 g / t, respectively; the lead selective collector is butyl xanthate, at a dosage of 35–50 g / t; and the frother is No. 2 oil, at a dosage of 12–20 g / t. In the first stage of the cleaning stage, the dosages are 150–200 g / t of sodium carbonate and 150–200 g / t of sodium thioglycolate. 200g / t, No. 2 oil 3~6g / t; second-stage refined sodium thioglycolate 80~100g / t, No. 2 oil 1~3g / t; first-stage, second-stage, and third-stage scavenging sodium sulfide dosages are 150~200g / t, 80~120g / t, and 40~60g / t respectively, butyl xanthate dosages are 8~12g / t, 4~8g / t, and 2~5g / t respectively, and No. 2 oil dosages are 2~4g / t, 1~3g / t, and 1~2g / t respectively.

4. The combined forward and reverse flotation beneficiation method for reducing lead content in copper concentrate as described in claim 1, characterized in that: In step three, based on the dry weight of crude copper concentrate, the amount of activated carbon added is 1000-1400 g / t, the stirring speed is 200-250 r / min, the stirring time is 8-12 min, and the slurry concentration in the de-agent process is 25%-30%.

5. The combined forward and reverse flotation beneficiation method for reducing lead content in copper concentrate as described in claim 1, characterized in that: In step four, the reverse flotation roughing pH adjuster is lime, with a dosage of 600–800 g / t; the lead mineral depressant is sodium humate and sodium thiosulfate, with dosages of 1000–1200 g / t and 500–600 g / t, respectively; the copper selective collector is ethyl thiocyanate Z-200, with a dosage of 25–35 g / t; and the frother is No. 2 oil, with a dosage of 12–18 g / t. In the first stage of cleaning, the lime dosage is 200–250 g / t, and the sodium humate dosage is 35 g / t. 0~400g / t, No. 2 oil 3~5g / t; second-stage refined sodium humate 150~200g / t, No. 2 oil 1~3g / t; first-stage, second-stage, and third-stage scavenging sodium thiosulfate dosages are 120~150g / t, 70~90g / t, and 30~50g / t respectively, Z-200 dosages are 5~8g / t, 3~5g / t, and 1~3g / t respectively, and No. 2 oil dosages are 2~4g / t, 1~3g / t, and 1~2g / t respectively.

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