Dressing and smelting combined process for recovering scheelite from gold flotation tailings

Abstract

A flotation enrichment process is adopted, modified sodium silicate is added into the gold flotation tailings, the floatability of target minerals is improved, selective inhibition on gangue minerals is enhanced, hydroximic acid and sodium oleate are used in a matched mode to serve as a composite collecting agent, and the recovery rate of scheelite is improved. The collecting capacity and selectivity of the collecting agent are improved, pre-enrichment of scheelite is achieved, and a tungsten rough concentrate product is obtained. And the rough concentrate, sodium carbonate and sodium hydroxide are evenly mixed according to a certain proportion and then roasted, CaWO4 is converted into Na2WO4 and Ca3WO6, and high-efficiency leaching of tungsten can be achieved by using water as a solvent for cinder at normal temperature and normal pressure.

Description

Technical Field

[0001] The invention belongs to the technical field of mineral processing, and particularly relates to a combined beneficiation and smelting process for recovering scheelite from gold flotation tailings Background Art

[0002] The average WO3 content in gold flotation tailings is 0.2-0.4%, and the highest can reach about 1%. The difficulties in tungsten recovery are mainly: ① The tailings have complex composition, high gangue mineral content, and low tungsten grade; ② The tungsten embedded in the tailings is fine in particle size, and it is closely associated with gangue minerals, which makes it difficult to separate and recover, and it is difficult to improve the grade of tungsten concentrate; ③ The tailings are stored for a long time, and the surface is oxidized to varying degrees, and the floatability difference is reduced. Therefore, separation and recovery are difficult; ④ The concentration process is often accompanied by high temperature and high pressure, which is difficult to operate.

[0003] For scheelite, the commonly used scheelite beneficiation methods currently used include the Petrov process, hydrochloric acid decomposition method, caustic soda leaching method, mechanical activation method, soda solution pressure cooking method and fluoride salt decomposition method. Due to the characteristics of poor, fine and mixed tailings, the beneficiation cost is high and the recovery rate is not high. It is difficult for the concentrate to meet the requirements of qualified products, the economic benefits are not ideal, and it is rarely used in practice.

[0004] Chongyi Zhangyuan Tungsten Co., Ltd. disclosed a technology for low-temperature leaching of scheelite using sulfuric acid or nitric acid-hydrochloric acid mixed acid and regeneration and recycling of incomplete calcium precipitation of acid leaching solution (CN116121566A). This technology not only achieves low-temperature and more thorough leaching of scheelite, but also improves the recovery rate of tungsten metal. Central South University disclosed a method for treating scheelite (CN108754123A), which is to mix scheelite with magnesium salt and then perform high-temperature roasting treatment; the obtained roasted sand is washed with water and then leached with acid or alkaline to obtain tungstic acid or tungstate solution; this method uses magnesium salt to transform CaWO4 in scheelite, which is difficult to be leached with acid and alkali, into MgWO4 that is easy to be leached with conventional acid and alkali at high temperature, thereby improving the leaching efficiency of scheelite. This method solves the problem of difficulty in extracting tungsten directly from calcium tungstate. Luoyang Luanchuan Molybdenum Co., Ltd. has disclosed a method for reducing soluble WO3 in scheelite leaching residue (CN107523688A). Through diaphragm plate and frame filter press filtration and multi-stage caustic soda countercurrent pressure washing in the machine, it can speed up the filtration and washing speed, improve work efficiency, reduce soluble WO3 in leaching residue, reduce tungsten loss, and improve tungsten recovery rate. It is suitable for large-scale promotion and application. Hunan Xiatung Metal Technology Co., Ltd. proposed a method for using sulfuric acid and phosphoric acid to synergistically decompose scheelite (CN104404249A). It uses continuous leaching combined with continuous acid replenishment to avoid fluctuations in scheelite leaching conditions and directly returns part of the leached slurry. On the one hand, it can further suppress fluctuations. On the other hand, the gypsum slag returned to the slurry under stable working conditions can be used as a seed, which simplifies the operation and improves the effect, thereby achieving large-scale stable production.

[0005] The similarities of the above technologies are that they all use hydrometallurgical processes. The difference is that the low-temperature leaching of scheelite with sulfuric acid or nitric acid-hydrochloric acid mixed acid and the incomplete calcium precipitation regeneration and recycling technology of the acid leaching solution (CN116121566A) and the method of synergistic decomposition of scheelite with sulfuric acid and phosphoric acid (CN104404249A) are all acidic leaching, which has certain requirements for the corrosion protection of equipment. A method for treating scheelite (CN108754123A) adopts a roasting-leaching combined process to achieve room temperature leaching of high-grade scheelite. A method for reducing soluble WO3 in scheelite leaching slag (CN107523688A) is alkaline leaching, but it is mainly aimed at residual soluble WO3 in the leaching slag. However, the above process does not involve the recovery of fine-grained low-grade scheelite in gold flotation tailings. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the object of the present invention is to provide a combined beneficiation and smelting process for recovering scheelite from gold flotation tailings, so as to achieve efficient recovery of fine-grained low-grade scheelite in gold flotation tailings.

[0007] In order to achieve the above-mentioned purpose, the present invention adopts a flotation enrichment method, firstly, a mixed depressant is used to achieve the selective inhibition of the gangue minerals therein, and a composite collector is used in combination to ensure the recovery rate of fine particles in the scheelite rough concentrate, thereby achieving the enrichment of scheelite in the gold flotation tailings and reducing the processing volume of the subsequent process. Then, the flotation rough concentrate product is roasted with sodium carbonate and sodium hydroxide to convert the insoluble CaWO4 into easily soluble Na2WO4 and Ca3WO6, so as to achieve the water leaching of scheelite at room temperature and pressure.

[0008] The specific technical solution adopted by the present invention is as follows:

[0009] A combined metallurgical process for recovering scheelite from gold flotation tailings comprises the following steps:

[0010] Step 1: flotation enrichment.

[0011] Step 2, alkaline roasting.

[0012] Step 3: water immersion at normal temperature and pressure.

[0013] The gold flotation tailings of the present invention are tungsten-containing tailings after gold selection, more than 97% of tungsten exists in the form of scheelite, the content of WO3 is 0.1-0.8%, -38μm fine tungsten is not less than 80%, the main gangue minerals are calcium gangue minerals, and other minerals have been oxidized on the surface due to long-term storage of tailings, showing surface properties similar to those of scheelite.

[0014] In step 1, the gold flotation tailings are flotated and enriched as follows:

[0015] Modified sodium silicate is added to the gold flotation tailings to improve the pH environment of the system and the floatability of the mineral surface, and combined with the use of composite sodium oleate as a collector to enhance the collector's collection ability and selectivity for flotation enrichment. The specific principles are as follows:

[0016] During the flotation enrichment process, modified sodium silicate is added:

[0017] Adjust the pH of the slurry to enhance the inhibitory effect of sodium silicate and the selectivity of the collector;

[0018] It reacts on the surface of calcareous gangue minerals to generate CaCO3, thereby inhibiting the calcareous gangue minerals.

[0019] Sodium silicate hydrolyzes and ionizes to produce Anions such as quartz and calcite cover the surface of gangue minerals, inhibiting the gangue minerals.

[0020] Make sodium silicate more Conversion, enhance the selective inhibition of gangue minerals, reduce the dosage of reagents, and reduce the viscosity of slurry.

[0021] Hydrolysis makes the solution highly alkaline, and the silicate film formed by sodium silicate is more stable, which effectively inhibits the flotation of gangue minerals such as quartz and calcite.

[0022] It has certain desliming and activation effects and can improve the flotation effect of scheelite.

[0023] In the flotation enrichment process, add composite sodium oleate:

[0024] Sodium oleate has a strong collection capacity and can improve the recovery rate of WO3 in the flotation enrichment of rough concentrate.

[0025] Hydroxamic acid has good selectivity and can enhance the recovery of fine-grained low-grade scheelite. Specifically: Hydroxamic acid can enhance the selective capture of fine-grained scheelite and reduce the WO3 content in the flotation enrichment tailings; the hydroxamic group (-C(=O)NHOH) in hydroxamic acid has high selectivity and can effectively inhibit the flotation of gangue minerals (such as quartz), thereby increasing the WO3 content in the flotation rough concentrate.

[0026] In addition, sodium oleate and hydroxamic acid can form a synergistic effect in the pulp to optimize the chemical environment of the pulp. Sodium oleate can adjust the surface tension of the pulp, and hydroxamic acid can stabilize the combination of the collector and the mineral surface, thereby improving the flotation efficiency.

[0027] The mixed use of sodium oleate and hydroxamic acid can reduce the dosage of a single collector, thereby reducing the flotation cost. The synergistic effect of the two reduces the total amount of collector required in the flotation process while ensuring the flotation effect.

[0028] Sodium oleate and hydroxamic acid have good collection effects in different pH ranges. Mixed use can expand the effective pH range of flotation, making the flotation process more flexible and stable, and convenient for actual production application.

[0029] In one embodiment, the flotation enrichment process can be a roughing and a scavenging process, and the rougher concentrate and the scavenger concentrate are combined as a rougher concentrate product to ensure that the recovery rate of tungsten in the rougher concentrate is not less than 80% and the WO3 content is 5% to 10%.

[0030] In one embodiment, the modified sodium silicate is composed of sodium carbonate and sodium silicate in a weight ratio of 3:5 to 4:5, and the composite sodium oleate is composed of hydroxamic acid and sodium oleate in a weight ratio of 0.2:1.5 to 0.3:1.5. Based on the weight of the original ore of the gold flotation tailings, the dosage of the modified sodium silicate is 4000-4500g / t, and the dosage of the composite sodium oleate is 1700-1800g / t.

[0031] In step 2, alkaline roasting refers to adding a certain proportion of sodium carbonate and sodium hydroxide to the coarse concentrate product obtained by flotation enrichment, mixing them evenly, and then roasting and pyrolyzing them at high temperature. The added sodium carbonate and sodium hydroxide work synergistically to achieve efficient decomposition of scheelite. The specific principles are as follows:

[0032] During the alkaline roasting process, sodium hydroxide and sodium carbonate are added:

[0033] Ca exists in the form of CaCO3 and CaO, resulting in a lower total amount of CaO in the slag than when NaOH is used alone for roasting, reducing the reverse precipitation of CaO.WO3 during the roasting-leaching process and increasing the decomposition rate of W. NaOH has a better decomposition effect on scheelite than Na2CO3, and the conversion rate of W when used in combination is higher than that when Na2CO3 is used alone.

[0034] ΔG of the reaction between CaWO4 and NaOH-Na2CO3 θT The smaller it is, the easier it is for the reaction to occur.

[0035] When NaOH-Na2CO3 is roasted together, it can promote the conversion of CaWO4 into Na2WO4 and Ca3WO6. The relative content of Na2WO4 with higher solubility in the slag is higher, while the content of CaWO4 with lower solubility is lower, thereby improving the roasting-leaching rate of scheelite.

[0036] NaOH is converted into a molten state at above 318.4°C, providing an excellent reaction environment for scheelite, NaOH and Na2CO3, increasing the effective contact between the reactants and thus improving the reaction efficiency.

[0037] In one embodiment, based on the weight of the coarse concentrate product, the dosage of sodium carbonate is 300-700 kg / t of sodium carbonate and sodium hydroxide, and the two are mixed and added in a ratio of 2:1.

[0038] In one embodiment, the alkaline calcination conditions are: 800-900° C. in air atmosphere for 1.5-3 h.

[0039] In step 3, the alkaline roasted product is placed in water for water leaching at room temperature and pressure, and the decomposition of residual alkaline compounds in the system is utilized to enhance the leaching of tungsten.

[0040] In one embodiment, the normal temperature and pressure water leaching refers to stirring and leaching the slag obtained after alkaline roasting with water under normal temperature and pressure conditions, with a leaching slurry liquid-to-solid ratio of 4:1-3:1 and a leaching time of 1-2 hours.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] 1. The new process of flotation enrichment-alkaline roasting-water leaching at room temperature and pressure is adopted to realize the leaching of scheelite at room temperature and pressure under alkaline conditions, which is simpler to operate and has lower requirements on equipment.

[0043] 2. Two new agents, modified sodium silicate and composite sodium oleate, were developed.

[0044] 3. The six functions of modified sodium silicate and composite sodium oleate are utilized to achieve efficient enrichment and recovery of fine-grained scheelite in gold flotation tailings, saving the dosage of reagents.

[0045] 4. Use sodium carbonate and sodium hydroxide to roast together to convert CaWO4 into easily hydrolyzed Na2WO4 and Ca3WO6.

[0046] 5. The water immersion of scheelite at normal temperature and pressure is realized, which is simple to operate and easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0048] The embodiments of the present invention are described in detail below with reference to the accompanying drawings and examples.

[0049] Tungsten in tailings is due to: ① complex composition, high content of gangue minerals, and low tungsten grade; ② fine particle size of tungsten in tailings, close coexistence with gangue minerals, difficult to separate and recover, and difficult to improve the grade of tungsten concentrate; ③ long-term storage of tailings, different degrees of oxidation on the surface, reduced floatability, so separation and recovery are difficult; ④ high temperature and high pressure are often accompanied by the beneficiation process, which is difficult to operate.

[0050] The present invention takes scheelite in the gold tailings as the target mineral, and ensures the recovery rate of WO3 in the rough concentrate by flotation enrichment. In the gold flotation tailings, modified sodium silicate is added to improve the floatability of the target mineral and enhance the selective inhibition of gangue minerals. Hydroxamic acid and sodium oleate are used as composite collectors to improve the collection capacity and selectivity of the collector, so as to achieve the pre-enrichment of scheelite and obtain a rough tungsten concentrate product. The rough concentrate is uniformly mixed with sodium carbonate and sodium hydroxide in a certain proportion and then roasted in coordination to convert CaWO4 into easily hydrolyzed Na2WO4 and Ca3WO6. A higher leaching rate can be achieved by water leaching the roasted slag under normal temperature and pressure conditions.

[0051] Specifically, Figure 1 As shown, the combined process for recovering scheelite from gold flotation tailings of the present invention mainly includes the following steps:

[0052] (1) Flotation tailing

[0053] Modified sodium silicate is added as an adjuster to the gold-containing tungsten tailings (specifically, it can be added to the slurry) to improve the floatability of the mineral surface, and a mixed collector is used in combination to enhance the collection ability and selectivity of the agent.

[0054] In the embodiment of the present invention, the flotation tailings discarding process is a one-roughing and one-scavenging process, and the rougher concentrate and the scavenger concentrate are combined as a rougher concentrate product to ensure the recovery rate of tungsten in the rougher concentrate.

[0055] In the embodiment of the present invention, the modified sodium silicate is prepared by sodium carbonate and sodium silicate in a mass ratio of 3:5 to 4:5, and the composite sodium oleate is a mixture of hydroxamic acid and sodium oleate in a mass ratio of 0.2:1.5 to 0.3:1.5. Based on the mass of the original ore, the dosage of the modified sodium silicate is 4000-4500g / t, and the dosage of the composite sodium oleate is 1700-1800g / t. The use of modified sodium silicate can effectively enhance the selective inhibition of calcium and silicon gangue minerals, improve the floatability difference between scheelite and gangue minerals, and use a composite collector of hydroxamic acid and sodium oleate to effectively improve the collection capacity of the collector, especially for fine-grained scheelite, enhance the selectivity of the collector to scheelite, improve the grade and recovery rate of the flotation coarse concentrate, and at the same time expand the system flotation pH range, improve the stability of the flotation index, and ensure the flexibility of the operation process.

[0056] In this step, by adding chemical regulators, the surface properties and flotation environment of gangue minerals and target minerals in gold flotation tailings are improved, and the efficient recovery of tungsten is achieved during the flotation enrichment process to ensure the recovery rate of tungsten. Specifically, its main principle and effect are as follows: by adding sodium carbonate to the gold flotation tailings slurry to modify sodium silicate, the pH of the slurry can be adjusted and the desludging effect can be achieved. Sodium silicate is hydrolyzed and ionized to produce Anions such as quartz and calcite cover the surface of gangue minerals, inhibiting the gangue minerals. It reacts on the surface of calcareous gangue minerals to generate CaCO3, which inhibits the formation of calcareous gangue minerals. Make sodium silicate more Conversion, enhancing the selective inhibition of gangue minerals, reducing the dosage of reagents, and lowering the viscosity of the slurry; Hydrolysis makes the solution present high alkalinity, and the silicate film formed by sodium silicate is more stable, which enhances the inhibitory effect of sodium silicate. Hydroxamic acid and sodium oleate are used together as composite collectors. The hydroxamic group (-C(=O)NHOH) in hydroxamic acid has high selectivity, and sodium oleate has strong collection ability. At the same time, it can adjust the surface tension of the slurry and optimize the chemical environment of the slurry. Hydroxamic acid can more stably bind the collector to the mineral surface. The synergistic effect of the two reduces the total amount of collector required in the flotation process and improves the flotation efficiency. The one-roughing and one-sweeping process is adopted to reduce the WO3 content in the tailings (tailings WO3≤0.2%) and ensure the recovery rate of tungsten in the flotation enrichment process. This process can obtain a tungsten coarse concentrate product with a WO3 content of more than 5% and a recovery rate of more than 80%.

[0057] (2) Alkaline roasting

[0058] Sodium carbonate and sodium hydroxide are added to the coarse concentrate obtained by flotation tailings, mixed evenly and then roasted together. The roasting temperature is 800-900°C and the roasting time is 2h. Based on the weight of the coarse concentrate enriched by tungsten flotation, the dosage of sodium carbonate is 400kg / t and the dosage of sodium hydroxide is 200kg / t.

[0059] In the embodiment of the present invention, the main effects are as follows: through the synergistic effect of sodium carbonate and sodium hydroxide, Ca exists in the form of CaCO3 and CaO, reducing the total amount of CaO in the slag and avoiding the reverse precipitation of CaO.WO3 during the roasting-leaching process; NaOH has a stronger alkalinity and is converted into a molten state at a temperature above 318.4°C, providing an excellent reaction environment for scheelite, NaOH and Na2CO3, increasing the effective contact between the reactants and improving the decomposition conversion rate of W. ΔG of the reaction of CaWO4 with NaOH-Na2CO3 θT Smaller, easier to react, accelerate the decomposition of scheelite, promote the conversion of CaWO4 to Na2WO4 and Ca3WO6, reduce the content of CaWO4 in slag, and improve the roasting conversion efficiency of scheelite. Finally, the decomposition conversion rate of CaWO4 in slag is >95%.

[0060] (3) Water immersion at normal temperature and pressure

[0061] After grinding the slag, it is immersed in water at room temperature and pressure with a liquid-to-solid ratio of 4:1. The residual carbonates and other alkaline compounds in the slag make the slurry present a higher alkalinity, while avoiding WO4 2- During the leaching process, CaO·WO3 is precipitated. The leaching time is 1-2 hours, and the leaching rate is more than 90%. The alkali in the lean liquid after the separation of the precious liquid can be recovered or reused.

[0062] The present invention selects gold tailings from different mining areas for experimental verification, and specific implementation data are shown in the following table.

[0063]

[0064] It can be seen that the combined beneficiation and smelting process for recovering scheelite from gold flotation tailings of the present invention achieves efficient separation and recovery of tungsten.

Claims

1. A combined metallurgical process for recovering scheelite from gold flotation tailings, characterized in that: The steps include: Step 1, flotation enrichment of gold flotation tailings, wherein the gold flotation tailings are tungsten-containing tailings after gold separation; Step 2, adding sodium carbonate and sodium hydroxide to the coarse concentrate product obtained by flotation enrichment for alkaline roasting to decompose the scheelite; Step 3: placing the alkaline roasted product in water for leaching at room temperature and pressure, and utilizing the decomposition of residual alkaline compounds in the system to enhance the leaching of tungsten.

2. The combined process for recovering scheelite from gold flotation tailings according to claim 1, characterized in that: In the gold flotation tailings, more than 97% of tungsten exists in the form of scheelite, the content of WO3 is 0.1-1%, and the -38μm fine tungsten is not less than 80%. The main gangue minerals are calcium gangue minerals, and other minerals are oxidized on the surface due to long-term storage, showing surface properties similar to those of scheelite.

3. The combined process for recovering scheelite from gold flotation tailings according to claim 1, characterized in that: In step 1, flotation enrichment of gold flotation tailings is carried out, and the implementation method is as follows: Modified sodium silicate is added to gold flotation tailings, and composite sodium oleate is used as a collector for flotation enrichment; the modified sodium silicate is composed of sodium carbonate and sodium silicate mixed in a weight ratio of 3:5 to 4:5, and the composite sodium oleate is composed of hydroxamic acid and sodium oleate mixed in a weight ratio of 0.2:1.5 to 0.3:1.

5.

4. The combined process for recovering scheelite from gold flotation tailings according to claim 3 is characterized in that: Based on the original ore weight of the gold flotation tailings, the dosage of the modified sodium silicate is 4000-4500 g / t, and the dosage of the composite sodium oleate is 1700-1800 g / t.

5. The combined metallurgical process for recovering scheelite from gold flotation tailings according to any one of claims 1 to 4, characterized in that: The flotation enrichment process is one roughing and one scavenging, and the roughing concentrate and the scavenging concentrate are combined as a rough concentrate product to ensure that the recovery rate of tungsten in the rough concentrate is not less than 80%.

6. The combined process for recovering scheelite from gold flotation tailings according to claim 1, characterized in that: In the step 2, based on the weight of the coarse concentrate product, sodium carbonate and sodium hydroxide are mixed and added in a ratio of 2:1, and the total amount is 300-700 kg / t.

7. The combined process for recovering scheelite from gold flotation tailings according to claim 1 or 6, characterized in that: The step 2 is calcining at 800-900° C. in an air atmosphere for 1.5-3 hours.

8. The combined process for recovering scheelite from gold flotation tailings according to claim 1, characterized in that: The step 3, water leaching at room temperature and pressure, refers to stirring and leaching the slag obtained after alkaline roasting with water under room temperature and pressure conditions. The operating conditions of the water leaching at room temperature are a leaching slurry liquid-to-solid ratio of 4:1-3:1 and a leaching time of 1-2 hours.

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