Method for recovering tungsten from alkali cooked slag of tungsten smelting

Abstract

The present application belongs to the technical field of tungsten smelting, and specifically discloses a method for recovering tungsten from alkali-cooked slag in tungsten smelting, which adopts a physical beneficiation method to recover tungsten in the slag, does not introduce a large amount of acid and alkali reagents, does not produce acid and alkali wastewater, does not need high-energy-consumption roasting or high-temperature acid and alkali leaching, and utilizes the physical differences such as particle size and density of the alkali-cooked slag to recover tungsten by gravity separation, so that the process is simple, large-scale treatment can be achieved, reagent consumption is low, energy consumption is low, water for beneficiation can be closed-circulated, no wastewater is discharged, the process is environmentally friendly and has no pollution risk, meanwhile, indexes of the alkali-cooked slag after harmless treatment can reach industrial solid waste, general solid waste is realized from hazardous waste, and environmental disposal cost is low.

Description

Technical Field

[0001] This invention belongs to the field of tungsten smelting technology, and specifically discloses a method for recovering tungsten from alkali boiling residue by gravity separation. Background Technology

[0002] my country ranks first in the world in terms of tungsten reserves, production, and exports. Depending on the tungsten ore raw material, the main process for producing ammonium paratungstate (APS) is sodium alkali pressure cooking, ion exchange / alkaline extraction, deep molybdenum removal, and evaporation crystallization. During the sodium alkali pressure cooking process in tungsten smelting, a large amount of tungsten-containing alkali cooking residue, also known as alkali-cooked tungsten slag or waste tungsten slag, is produced. Based on the 2024 APT production of 130,000 tons, approximately 100,000 to 120,000 tons of alkali cooking residue are produced annually. This residue mainly consists of iron, manganese, and calcium oxides, and also contains high-value metal elements such as W, Sn, Ta, Nb, and Sc, as well as harmful elements such as As, Pb, Cr, and F. Due to its high As content and leaching toxicity, in 2016, the Ministry of Environmental Protection of China included "alkali cooking residue (tungsten slag) generated during the alkali decomposition of APS in the production process" in the "National Hazardous Waste List." Therefore, under the dual pressure of comprehensive resource utilization and environmental protection, how to achieve the reduction, resource utilization, and harmless disposal of tungsten slag is of great significance to the sustainable development of my country's tungsten smelting industry.

[0003] Due to limitations in the technological level of tungsten smelting units, the WO3 content in alkali-boiled tungsten slag varies from 0.5% to 5%, resulting in a waste of approximately 2,000-3,000 tons of tungsten metal resources annually. Currently, the commonly used method is high-temperature sintering with soda followed by water leaching to treat the alkali-boiled tungsten slag, which can reduce the WO3 content in the slag to below 0.5%. However, the amount of soda consumed during the process is very high, the roasting process is energy-intensive, and the environmental treatment costs for waste gas and wastewater are high. Another method is to use a secondary high-temperature alkaline pressure cooking process to treat waste tungsten slag, which can reduce the tungsten content of the waste tungsten slag from 3% to 0.5-1%. However, similar to the high-temperature sintering with soda, this method also suffers from excessive alkali consumption and high energy consumption. In addition, the alkali process for recovering tungsten from alkali-boiled slag is energy-intensive and consumes a large amount of alkali, and is generally only suitable for treating high-grade tungsten slag with a WO3 content of 3% to 6%.

[0004] Some tungsten smelting units have explored using an acid process at room temperature and pressure to recover tungsten from tungsten slag using hydrochloric acid and sulfur-phosphorus mixed acid. After leaching, the tungsten is enriched and impurities are removed using a weakly basic anion exchange resin, reducing the tungsten content in the slag to 0.5-1%. However, since the tungsten grade in the slag is lower than that in tungsten concentrate, both acid and alkaline processes require a large amount of acid and alkaline reagents for tungsten recovery. The enrichment of low-concentration tungsten solutions is accompanied by a large amount of wastewater and waste gas that requires environmental treatment, resulting in relatively high costs. Summary of the Invention

[0005] To address the problems in the background art, this invention discloses a method for recovering tungsten from alkali smelting slag by gravity separation. The method utilizes the differences in physical properties such as particle size and density of the alkali smelting slag for gravity separation to recover tungsten. This physical beneficiation method for recovering tungsten from alkali smelting slag requires fewer reagents, has a simple operation, and low processing costs. Furthermore, the gravity-separated tungsten slag is converted from hazardous waste to general solid waste after harmless treatment.

[0006] To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] A method for recovering tungsten from alkali boiling residue by gravity separation, characterized by comprising the following steps:

[0008] (1) The slag from tungsten smelting alkali boiling is mixed with ore and slurry is prepared by adding an oxidizing dispersant and a defoamer at the same time as the slurry preparation.

[0009] (2) The slurry obtained in step (1) is classified by wet screening or hydrocyclone to obtain coarse and fine particles;

[0010] (3) The fine particles obtained in step (2) are separated and enriched by a blanket concentrator to obtain coarse concentrate and coarse tailings;

[0011] (4) The coarse particles obtained in step (2) and the coarse concentrate obtained in step (3) are mixed and then subjected to secondary separation and enrichment on a shaking table to obtain shaking concentrate, shaking medium ore and shaking tailings respectively. The shaking concentrate is filtered to obtain low-grade tungsten concentrate. The low-grade tungsten concentrate is returned to the tungsten smelting process, and the shaking medium ore is returned to the shaking table for further separation.

[0012] (5) The tailings obtained in step (4) are scavenged by a blanket beneficiator to obtain scavenged concentrate and tailings. The scavenged concentrate is returned to step (4) and further separated and enriched by a shaking table.

[0013] (6) Combine the coarse tailings obtained in step (3) and the scavenged tailings obtained in step (5), adjust the pH, add heavy metal removal agent and flocculant for harmless treatment, and then filter press to obtain industrial solid waste and filter press circulating water. After static sedimentation, the filter press circulating water is returned to the slurry preparation process for closed-loop circulation.

[0014] Furthermore, in the method for recovering tungsten by gravity separation of alkali slag from tungsten smelting, step (1) involves the WO3 content in the alkali slag from tungsten smelting being 0.5-5%, the WO3 mass percentage content being controlled to not exceed ±0.5% during the ore blending process, and the mass percentage concentration of the alkali slag slurry from tungsten smelting being adjusted to 10-20%.

[0015] Furthermore, in the method for recovering tungsten by gravity separation of alkali slag in tungsten smelting, the oxidizing dispersant is an inorganic sulfate, added at a rate of 0.5-2‰ of the ore weight, and the defoamer is an organosilicon defoamer used in mineral processing, added at a rate of 0.5-2 kg / t.

[0016] Furthermore, in the method for recovering tungsten from alkali slag by gravity separation, step (2) involves wet screening or pre-classification using a 120-325 mesh screen or hydrocyclone according to the particle size of the alkali slag. The mass of coarse particles is 10-30% of the total slurry mass, and the enrichment ratio of WO3 grade in the coarse particles is 1.5-3.

[0017] Furthermore, in the method for recovering tungsten by gravity separation of alkali slag in tungsten smelting, the number of tandem stages of blanket beneficiation in steps (3) and (5) is 3-10, the mass percentage concentration of the ore pulp is 10-20%, and the WO3 grade enrichment ratio of the concentrate in the roughing stage of step (3) and the scavenging stage of step (5) is 1.2-3 respectively.

[0018] Furthermore, in the method for recovering tungsten by gravity separation of alkali slag in tungsten smelting, the mass percentage concentration of the slurry fed into the shaking table in step (4) is 15-30%, and the grade of the low-grade tungsten concentrate obtained is 10-30%.

[0019] Furthermore, in the method for recovering tungsten from alkali slag by gravity separation, step (6) harmless treatment refers to adding sulfuric acid, nitric acid, oxalic acid or organic acid to the tailings to adjust the pH value to 6-9. According to the difference in heavy metal pollution and toxicity in the alkali slag, ferrous sulfate and PAC are added to remove harmful elements such as As, Pb, Cr, and F. Depending on the content of arsenic and chromium in the treated alkali slag, an appropriate amount of ammonium persulfate or hydrogen peroxide is added to react and precipitate the remaining arsenic. Finally, PAM is added for two-stage thickening flocculation. After harmless treatment, the gravity separation tungsten slag slurry is filtered to obtain industrial solid waste and filter press circulating water, so that the alkali slag becomes industrial waste without hazardous characteristics. The filter press circulating water is returned to the system for recycling after sedimentation and settling. When the tungsten in the circulating water reaches a certain concentration, it is recovered by ion exchange and then evaporated.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention relates to a method for recovering tungsten from alkali slag by gravity separation. This method employs physical beneficiation to recover tungsten from the slag, without introducing large amounts of acid or alkali reagents, generating no acid or alkali wastewater, and eliminating the need for energy-intensive roasting or high-temperature acid-alkali leaching. It utilizes physical differences in particle size and density of the alkali slag for gravity separation to recover tungsten. The process is simple, suitable for large-scale processing, consumes few reagents and has low energy consumption, and allows for closed-loop recycling of beneficiation water, resulting in no wastewater discharge. The process is environmentally friendly and poses no pollution risk. After harmless treatment, the alkali slag meets the standards for industrial solid waste, and environmental disposal costs are low. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a process flow diagram of the method for recovering tungsten from alkali boiling residue by gravity separation in tungsten smelting according to the present invention. Detailed Implementation

[0024] To better understand the present invention, the following embodiments further illustrate the content of the invention, but the scope of protection of the present invention is not limited to the following embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0025] Example 1

[0026] In this example, the raw material is slag from scheelite boiled with soda and tungsten slag boiled with alkali. The tungsten content, calculated in WO3 form, is 0.94% (mass percentage). The main components are calcium tungstate, iron tungstate, calcium carbonate, calcium phosphate, silicon dioxide, calcium fluoride and other mineral phases.

[0027] Step (1): Add circulating water to the alkali-cooked tungsten slag after pressure filtration to adjust the slurry concentration to 14-18%, and add 1‰ of the mineral amount of sulfate oxidizing dispersant and 0.5-2kg / t of mineral beneficiation defoamer. Adjust the amount of mineral beneficiation defoamer according to the foam situation. After adjusting the slurry, use basket filtration to disperse the particles.

[0028] Step (2): The slurry is screened through a 200-mesh wet screen to pre-separate coarse and fine particles, respectively obtaining coarse particles and fine particles. The coarse particles account for about 15-30%, and the tungsten content enrichment ratio is about 2.

[0029] Step (3): The fine particle concentration in step (2) is controlled at 13-17%, and 5-stage blankets are used for series recovery to obtain coarse concentrate and coarse tailings. The tungsten content enrichment ratio of the coarse concentrate is 1.5-2.5, and the tungsten content of the coarse tailings is less than 0.4%.

[0030] Step (4): The coarse particles from step (2) and the medium concentrate from step (3) are fed into different shaking tables. The mass percentage concentration of the slurry is 15-20%, resulting in a low-tungsten shaking concentrate with a tungsten content of 15-20%. The actual tungsten recovery rate based on the shaking concentrate is 44.8%. The middlings are returned to the shaking table for further separation.

[0031] Step (5): The tailings from step (4) are fed into a 5-stage series scavenging blanket to obtain scavenged concentrate and scavenged tailings. The tungsten enrichment ratio of the scavenged concentrate is 1.5-2.5, and the tungsten content of the scavenged tailings is less than 0.5%.

[0032] Step (6): The coarse tailings obtained in step (3) and the tailings slurry obtained in step (5) are combined, sulfuric acid is added to adjust the pH value to 8-9, ferrous sulfate and PAC are added to remove harmful elements such as As, Pb, Cr, and F, and the tailings are filtered after PAM flocculation. The tungsten content in the filter residue is less than 0.5%, the leaching toxicity is less than the relevant requirements of the national standard GB5085, and the turbidity of the filter water after standing is less than 200 NTU and returned to leaching.

[0033] Example 2

[0034] In this example, the raw material is slag from scheelite boiled with soda and tungsten slag boiled with alkali. The tungsten content, calculated in WO3 form, is 1.59% (mass percentage). The main components are calcium tungstate, iron tungstate, calcium carbonate, calcium phosphate, silicon dioxide, calcium fluoride and other mineral phases.

[0035] Step (1): Add circulating water to the alkali-cooked tungsten slag after pressure filtration to adjust the slurry concentration to 13-18%, and add sulfate dispersant and mineral processing defoamer. The amount of sulfate dispersant is 1‰ of the mineral amount, and the amount of mineral processing defoamer is 0.5-2 kg / t. Adjust the amount of mineral processing defoamer according to the foam situation. After slurry adjustment, the slurry is dispersed by basket filtration and there are no particulate matter.

[0036] Step (2): The slurry is pre-sorted by hydrocyclones to obtain coarse and fine particles. Among them, coarse particles with a mesh size of 200 or larger account for about 20-30%, and the tungsten enrichment ratio is greater than 1.5.

[0037] Step (3): The fine particle concentration in step (2) is controlled at 13-17%, and 5-stage blankets are used for series recovery to obtain coarse concentrate and coarse tailings. The tungsten content enrichment ratio of the coarse concentrate is 1.2-2.5, and the tungsten content of the coarse tailings is less than 0.5%.

[0038] Step (4): The coarse particles from step (2) and the medium-coarse concentrate from step (3) are respectively fed into different shaking tables for classification, with a concentration of 15-20%, to obtain low-grade tungsten concentrate with a tungsten content of 15-25%. The actual tungsten recovery rate based on the concentrate is 59.7%. The medium-coarse concentrate is returned to the shaking table for further separation.

[0039] Step (5): In step (4), the tail is fed into a 10-stage series scavenging blanket to obtain scavenged concentrate and scavenged tailings. The tungsten enrichment ratio of the scavenged concentrate is 1.5-2.5, and the tungsten content of the scavenged tailings is less than 0.6%.

[0040] Step (6): Add sulfuric acid to the coarse tailings from step (3) and the sludge from step (5) to adjust the pH value to less than 9, add ferrous sulfate + PAC to remove heavy metals and fluorine, PAM to flocculate and precipitate, filter the tailings, the tungsten content in the filter residue is less than 0.5%, the leaching toxicity is less than the relevant requirements of the national standard GB5085, and the turbidity of the filter water after standing is less than 200 NTU and returned to leaching.

[0041] Example 3

[0042] The raw materials used in Example 3 are the same as those used in Example 1, and steps (1)-(5) in Example 3 are the same as those in Example 1;

[0043] Step (6): Combine the coarse tailings obtained in step (3) and the tailings slurry obtained in step (5), add sulfuric acid to adjust the pH value to 8-9, and use the returned circulating water to prepare a ferrous sulfate + PAC mixed solution. The amount of ferrous sulfate is 1.5-2% of the ore weight, the amount of PAC is 0.7-2‰ of the ore weight, and the solution concentration is 5-10%. After mixing with the tailings slurry pipeline, react. Depending on the content of arsenic and chromium, add ammonium persulfate or hydrogen peroxide oxidant to achieve precipitation and removal of heavy metals As, Pb, Cr and fluorine. Prepare 1‰ PAM (adjust the amount according to the flocculation and purification situation) and add it to the two-stage thickener for flocculation and settling. After thickening, the underflow is filtered. The tungsten content in the filter residue is less than 0.5%, and the leaching toxicity test of the filter residue is less than the relevant requirements of the national standard GB5085. At the same time, the turbidity of the filter water and the overflow water of the two-stage thickener after settling is less than 200 NTU and returned for leaching.

[0044] Example 4

[0045] In this example, the raw material is slag from scheelite boiled with soda and tungsten slag boiled with alkali. The tungsten content, calculated in WO3 form, is 4.58% (mass percentage). The main components are calcium tungstate, iron tungstate, calcium carbonate, calcium phosphate, silicon dioxide, calcium fluoride and other mineral phases.

[0046] Step (1): Add circulating water to the alkali-cooked tungsten slag after pressure filtration to adjust the slurry concentration to 13-18%, and add sulfate dispersant and mineral processing defoamer. The amount of sulfate dispersant is 1‰ of the mineral amount, and the amount of mineral processing defoamer is 0.5-2 kg / t. Adjust the amount of mineral processing defoamer according to the foam situation. After slurry adjustment, the slurry is dispersed by basket filtration and there are no particulate matter.

[0047] Step (2): The slurry is pre-sorted by hydrocyclones to obtain coarse and fine particles. Among them, coarse particles with a mesh size of 200 or larger account for about 20-30%, and the tungsten enrichment ratio is greater than 1.5.

[0048] Step (3): The fine particle concentration in step (2) is controlled at 13-17%, and 5-stage blankets are used for series recovery to obtain coarse concentrate and coarse tailings. The tungsten content enrichment ratio of the coarse concentrate is 1.2-2.5, and the tungsten content of the coarse tailings is less than 0.6%.

[0049] Step (4): The coarse particles from step (2) and the medium-coarse concentrate from step (3) are fed into different shaking tables for classification, with a concentration of 13-20%, to obtain low-grade tungsten concentrate with a tungsten content of 15-25%. The actual tungsten recovery rate based on the concentrate is 82.4%. The medium-coarse concentrate is returned to the shaking table for further separation.

[0050] Step (5): In step (4), the tail is fed into a 10-stage series scavenging blanket to obtain scavenged concentrate and scavenged tailings. The tungsten enrichment ratio of the scavenged concentrate is 1.2-2.5, and the tungsten content of the scavenged tailings is less than 0.8%.

[0051] Step (6): Add sulfuric acid to the coarse tailings from step (3) and the sludge from step (5) to adjust the pH value to less than 9, add ferrous sulfate + PAC to remove heavy metals and fluorine, PAM to flocculate and precipitate, filter the tailings, the tungsten content in the filter residue is less than 0.8%, the leaching toxicity is less than the relevant requirements of the national standard GB5085, and the turbidity of the filter water after standing is less than 200 NTU and returned to leaching.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for recovering tungsten from alkali slag by gravity separation, characterized in that, Includes the following steps: (1) The slag from tungsten smelting alkali boiling is mixed with ore and slurry, and an oxidizing dispersant and a defoamer are added at the same time as the slurry is prepared; (2) The slurry obtained in step (1) is pre-sorted by wet screening or hydrocyclone to obtain coarse and fine particles; (3) The fine particles obtained in step (2) are separated by a blanket beneficiator to obtain coarse concentrate and coarse tailings; (4) The coarse particles obtained in step (2) and the coarse concentrate obtained in step (3) are mixed and then subjected to secondary separation and enrichment on a shaking table to obtain shaking concentrate, shaking middlings and shaking tailings respectively. The shaking concentrate is filtered to obtain low-grade tungsten concentrate. The low-grade tungsten concentrate is returned to the tungsten smelting process, and the shaking middlings are returned to the shaking table for further separation. (5) The tailings obtained in step (4) are scavenged by a blanket beneficiator to obtain scavenged concentrate and scavenged tailings. The scavenged concentrate is returned to step (4) and further separated and enriched by a shaking table. (6) Combine the coarse tailings obtained in step (3) and the scavenged tailings obtained in step (5), add sulfuric acid, nitric acid, oxalic acid or organic acid to the tailings to adjust the pH value to 6-9, and add ferrous sulfate and PAC to remove heavy metals and fluorine, depending on the difference in heavy metal pollution and toxicity in the alkaline cooking residue, to remove harmful elements such as As, Pb, Cr and F. Depending on the content of arsenic and chromium in the alkaline cooking residue after treatment, add an appropriate amount of ammonium persulfate or hydrogen peroxide to react and precipitate the remaining arsenic. Finally, add PAM for two-stage thickening flocculation. After the tungsten slag slurry is treated harmlessly, it is filtered to obtain industrial solid waste and filter press circulating water. The filter press circulating water is returned to the system for recycling after sedimentation and settling. When the tungsten in the circulating water reaches a certain concentration, it is recovered by ion exchange and then evaporated.

2. The method for recovering tungsten from alkali slag by gravity separation according to claim 1, characterized in that, Step (1) The mass percentage of WO3 in the alkali slag of tungsten smelting is 0.5-5%. During the ore blending process, the mass percentage of WO3 should be controlled to not exceed ±0.5%. The mass percentage concentration of the alkali slag slurry of tungsten smelting should be adjusted to 10-20%.

3. The method for recovering tungsten from alkali slag by gravity separation according to claim 1, characterized in that, The oxidizing dispersant is an inorganic sulfate, and the amount of dispersant added is 0.5-2‰ of the ore weight. The defoamer is a mineral processing defoamer, and the amount added is 0.5-2 kg / t.

4. The method for recovering tungsten from alkali slag by gravity separation according to claim 1, characterized in that, Step (2) Wet screening or hydrocyclone pre-classification is performed on the alkaline residue using a 120-325 mesh screen according to the particle size. The mass of coarse particles is 10-30% of the total slurry mass, and the WO3 enrichment ratio in the coarse particles is 1.5-3.

5. The method for recovering tungsten from alkali slag by gravity separation according to claim 1, characterized in that, The number of tandem stages in the blanket beneficiation process in steps (3) and (5) is 3-10, the mass percentage concentration of the slurry is 10-20%, and the WO3 grade enrichment ratio of the concentrate in the roughing and scavenging steps is 1.2-3.

6. The method for recovering tungsten from alkali slag by gravity separation according to claim 1, characterized in that, In step (4), the mass percentage concentration of the slurry fed into the shaking table is 15-30%, and the grade of the resulting low-grade tungsten concentrate is 10-30%.

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