Dressing and smelting combined comprehensive utilization process for tailings subjected to sparse separation

Abstract

The invention provides a beneficiation-metallurgy combined comprehensive utilization process for dilute separation tailings, which comprises the following steps: carrying out ore grinding and flotation treatment on the dilute separation tailings to obtain fluorite rough concentrate and flotation tailings; magnetically roasting the mixed reducing agent and the flotation tailings, and magnetically separating to obtain magnetically separated rough concentrate and magnetically separated rough tailings; carrying out fine grinding and magnetic separation on the magnetic separation rough concentrate to obtain a magnetic separation iron concentrate product and magnetic separation concentrate tailings; the magnetic separation coarse tailings and the magnetic separation fine tailings are mixed, and then acid washing liquid and acid washing residues are obtained after acid washing and solid-liquid separation are conducted in sequence; and carrying out pressurized acid leaching, solid-liquid separation and extraction on the pickling residues to obtain scandium oxide and niobium oxide. By adopting the flotation-magnetizing roasting-magnetic separation-acid pickling-pressurized acid leaching combined process, the fluorite coarse ore, the iron ore concentrate, the rare earth leaching solution and the niobium-scandium leaching solution are obtained, the comprehensive utilization rate of the tailings is greatly increased, the discharge amount of the tailings is reduced, the acid consumption of tailings treatment is reduced, the environmental pressure is reduced, and the benefits of enterprises are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of comprehensive recycling and utilization of rare earth tailings, and particularly relates to a combined beneficiation and smelting comprehensive utilization process for rare earth beneficiation tailings. Background Art

[0002] The increasing demand for green technologies has led to the application of rare earths in the field of advanced electronic products, increasing the demand for rare earth elements in major economies around the world, including the United States, the European Union, the United Kingdom, and Japan, with an estimated annual growth rate of 3.7 - 8.6%. These countries have adjusted the global rare earth supply chain to stimulate rare earth production. High-grade rare earth element deposits are being depleted, and China, the country with the richest rare earth resources in the world, has seen a sharp decline in reserves in the past 50 years. Therefore, there is an urgent need for practical technologies to effectively recover rare earth resources from a large amount of rare earth tailings with high rare earth content.

[0003] The Bayan Obo tailings reservoir, known as the world's largest rare earth element tailings reservoir, has been receiving tailings from mineral production at a rate of 386,000 t / a since the 1960s. Currently, the tailings pond covers an area of approximately 12 km 2 and has accumulated approximately 200 million tons of rare earth tailings. Due to its high content of iron, rare earth, fluorine, Nb, and other elements, it is a valuable secondary resource with high utilization value. However, due to its low grade, fine dissemination size, complex mineral composition and symbiotic relationship, it is difficult to recycle. Currently, the utilization of Bayan Obo tailings is still in the laboratory research stage, and the main methods for treating Bayan Obo tailings include physical separation treatment, hydrometallurgical treatment, and pyrometallurgical treatment. In a typical Bayan Obo tailings treatment process, physical operations such as grinding, screening, magnetic separation, flotation, gravity separation, and density-based separation are used as pretreatment to release and concentrate the metal part and the non-metal part.

[0004] Currently, the research on the utilization of tailings mainly focuses on the recovery of minerals such as fluorite, iron, niobium, and rare earth in the tailings. For example, CN 110860369A discloses a method for recovering ultra-low grade rare earth and fluorite from rare earth tailings. By carrying out the combined flotation of rare earth and fluorite on the tailings, magnetic separation of the combined flotation concentrate, and fluorite flotation of the magnetic separation tailings, fluorite concentrate and rare earth concentrate are obtained. CN 103263977A discloses a process for recovering iron and rare earth from weakly magnetic tailings in Baotou. By using a one-rough-three-clean flotation process for the weakly magnetic tailings, rare earth concentrate with a grade greater than 50% is obtained, and the rare earth tailings are then subjected to magnetic separation and flotation to obtain iron concentrate with a grade greater than 62%. CN 103831173A discloses a process method for improving the rare earth recovery rate and fluorite grade in tailings. By carrying out one-rough-multi-clean combined flotation and one-rough-multi-clean fluorite flotation on the tailings, fluorite concentrate with a grade above 97% is obtained.

[0005] CN 111363912 A discloses a method for comprehensively utilizing rare earth tailings. This method first mixes the tailings with inorganic substances containing calcium chloride to obtain a mixed material, and then calcines the mixed material. The flue gas from the calcination is condensed to obtain a product containing niobium chloride; the calcined slag is leached with water to obtain a rare earth chloride solution; the water-leached slag is further finely ground and subjected to magnetic separation in two stages to obtain iron concentrate; the mixed tailings are further leached with hydrochloric acid to obtain a solution containing scandium chloride. This method realizes the separate recovery of iron, rare earth, niobium and scandium.

[0006] CN 115814936 A discloses a process for the combined comprehensive utilization of rare earth tailings beneficiation and smelting. This process first performs gravity separation and desliming pretreatment on rare earth tailings to obtain coarse ore and tailings; the coarse ore is subjected to bulk flotation to obtain bulk flotation concentrate and bulk flotation tailings; then, gum rosin flotation reagents and strontium-barium inhibitors are used to separate and float the bulk flotation concentrate to obtain rough fluorite ore and flotation tailings; the flotation tailings are further subjected to gravity separation and magnetic separation to obtain rare earth concentrate and strontium-barium concentrate.

[0007] However, according to the process mineralogy of the tailings, a method for comprehensively utilizing low-grade fluorite, iron, rare earth, niobium and scandium resources in rare earth beneficiation tailings has not been reported yet. Summary of the Invention

[0008] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a combined comprehensive utilization process for rare earth beneficiation tailings. The present invention adopts a combined process of flotation - magnetization roasting - magnetic separation - pickling - pressure acid leaching to obtain rough fluorite ore, iron concentrate, rare earth leaching solution, niobium and scandium leaching solution, greatly improving the comprehensive utilization rate of tailings, reducing the discharge of tailings, reducing the acid consumption for tailings treatment, reducing the environmental pressure, and enhancing the benefits of enterprises.

[0009] To achieve this purpose, the present invention adopts the following technical solutions:

[0010] The present invention provides a combined comprehensive utilization process for rare earth beneficiation tailings, and the process comprises the following steps:

[0011] (1) Grinding and flotation treatment are carried out on rare earth beneficiation tailings to obtain rough fluorite concentrate and flotation tailings;

[0012] (2) A reducing agent is mixed with the flotation tailings obtained in step (1) for magnetization roasting and magnetic separation to obtain magnetic separation rough concentrate and magnetic separation rough tailings;

[0013] (3) The magnetic separation rough concentrate obtained in step (2) is sequentially finely ground and subjected to magnetic separation to obtain a magnetic separation iron concentrate product and magnetic separation fine tailings;

[0014] (4) The magnetic separation rough tailings obtained in step (2) and the magnetic separation fine tailings obtained in step (3) are mixed, and then pickling and solid-liquid separation are carried out in sequence to obtain pickling solution and pickling slag;

[0015] (5) The pickling residue obtained in step (4) is subjected to pressure acid leaching, followed by solid-liquid separation and extraction to obtain scandium oxide and niobium oxide.

[0016] It should be noted that the lean ore tailings described in the present invention are selected from the Bayan Obo lean ore tailings in Baotou area, Inner Mongolia. In addition to rare earths, valuable minerals such as fluorite, iron, niobium, and scandium are associated with the lean ore tailings. The rare earth grade in the tailings is 3-6%, the fluorite grade is 20-30%, the iron oxide content is 20-30%, the niobium oxide content is 0.1-0.2%, and the scandium oxide content is 150-250 ppm. Although the contents of niobium and scandium are very low, their values are huge. Therefore, only by comprehensively utilizing the fluorite, iron, rare earths, and niobium in the tailings can the value of the tailings be maximally utilized.

[0017] In addition, the Bayan Obo lean ore tailings selected in the present invention have the following characteristics: (1) The particle size of the lean ore tailings is small. The ore particles of -200 mesh account for more than 75% of the total amount of the tailings, the ore particles of -300 mesh account for more than 55% of the total amount of the tailings, and the ore particles of -500 mesh account for more than 35% of the total amount of the tailings, which is not conducive to flotation treatment; (2) The fluorite, hematite, bastnasite, etc. in the lean ore tailings have been contaminated by rare earth ore dressing reagents, which will seriously affect the dosage and selection of flotation reagents during re-flotation; (3) More than 97% of the F in the lean ore tailings exists in fluorite minerals, but only about 60% of the iron exists in hematite, and the remaining iron exists in aegirine, aegirine-augite, pyrite, and siderite, making the recovery difficult and the recovery cost high; (4) The niobium in the lean ore tailings mainly exists in minerals such as pyrochlore and columbite. The symbiotic relationship of these minerals in the tailings is complex, the degree of dissociation is lower than 50%, and the content is low, resulting in a high recovery cost; (5) The scandium in the lean ore tailings mainly exists in silicate minerals such as aegirine and aegirine-augite and columbite in the form of isomorphism, and the content is low. The decomposition of silicate minerals is difficult and the recovery is difficult.

[0018] The combined comprehensive utilization process provided by the present invention can effectively overcome the characteristics of the lean ore tailings themselves. Through the combined process of flotation - magnetization roasting - magnetic separation - pickling - pressure acid leaching, fluorite rough concentrate, iron concentrate, rare earth leaching solution, and niobium and scandium leaching solution are effectively obtained, realizing the comprehensive utilization of the lean ore tailings.

[0019] As a preferred technical solution of the present invention, the end point of the grinding in step (1) is that the particle size of the lean ore tailings is -200 mesh accounting for more than 95 wt%, for example, it can be 95 wt%, 96 wt%, 97 wt%, 98 wt%, or 99 wt%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0020] It should be noted that in the present invention, the particle size of the tailings is limited to -200 mesh through grinding. If the particle size is too small, it is not conducive to subsequent flotation treatment and the precise separation of fluorite rough concentrate and flotation tailings.

[0021] Furthermore, the purpose of limiting the proportion of tailings with a particle size of -200 mesh to more than 95% through grinding before flotation treatment in the present invention is as follows: Although the proportion of the dilute-selected tailings with a particle size below -500 mesh accounts for more than 35% in the present invention, the dissociation degree of fluorite is only 75%. Moreover, among the tailings with a particle size above +200 mesh, the dissociation degree of fluorite is the lowest. Therefore, it is necessary to finely grind the tailings again to improve the dissociation degree of fluorite, and also to expose the surface of new minerals, reducing the influence of flotation reagent pollution.

[0022] Preferably, the flotation treatment includes at least one rough selection and three fine selections.

[0023] Preferably, the process further includes refining the fluorite rough concentrate in step (1) to obtain a fluorite product.

[0024] As a preferred technical solution of the present invention, the flotation reagents used in the flotation treatment include sodium oleate, inhibitors, and dextrin.

[0025] Preferably, the inhibitors include sodium metasilicate, sodium carbonate, and dextrin.

[0026] It should be noted that in the flotation treatment, fluorite rough concentrate can be effectively flotated. Sodium oleate is selected as a conventional flotation reagent. However, since it is necessary to enrich rare earth minerals and iron minerals in the tailings, sodium metasilicate and dextrin inhibitors need to be added. These two inhibitors can effectively inhibit silicate minerals, rare earth minerals, and iron minerals, improve the grade of fluorite flotation concentrate, and effectively enrich rare earth, iron minerals, and niobium minerals in the tailings. In addition, sodium metasilicate and dextrin need to act in an alkaline environment. Therefore, sodium carbonate needs to be added to adjust the environmental pH.

[0027] Preferably, the content of sodium oleate in the flotation reagent is 200 - 600 g / t. For example, it can be 200 g / t, 300 g / t, 400 g / t, 500 g / t, or 600 g / t, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0028] Preferably, the content of sodium metasilicate in the flotation reagent is 400 - 800 g / t. For example, it can be 400 g / t, 500 g / t, 600 g / t, 700 g / t, or 800 g / t, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0029] Preferably, the content of sodium carbonate in the flotation reagent is 200-700 g / t. For example, it can be 200 g / t, 300 g / t, 400 g / t, 500 g / t, 600 g / t or 700 g / t, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0030] Preferably, the content of dextrin in the flotation reagent is 200-700 g / t. For example, it can be 200 g / t, 300 g / t, 400 g / t, 500 g / t, 600 g / t or 700 g / t, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0031] As a preferred technical solution of the present invention, the reducing agent in step (2) includes charcoal powder and / or graphite powder.

[0032] Preferably, the addition amount of the reducing agent in step (2) is 0.5-2.5% of the mass of the flotation tailings. For example, it can be 0.5%, 0.9%, 1.3%, 1.7%, 2.1% or 2.5%, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0033] As a preferred technical solution of the present invention, the temperature of the magnetization roasting in step (2) is 500-800 °C. For example, it can be 500 °C, 550 °C, 600 °C, 650 °C, 700 °C, 750 °C or 800 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0034] The magnetization roasting of the present invention can not only reduce hematite in the flotation tailings to magnetite with strong magnetism, but also during the roasting process, the main occurring mineral of rare earth, bastnasite, will decompose to generate a product of CeOF, which can react in dilute acid to generate a soluble rare earth salt solution. The temperature of the magnetization roasting is 500-800 °C. If the temperature is too high, it will lead to over-magnetization, a large amount of FeO will appear in the product, resulting in weakened magnetism and increased energy consumption; if the temperature is too low, it will lead to insufficient magnetization, and Fe2O3 in the product cannot be effectively converted into Fe3O4, affecting the recovery rate of Fe.

[0035] Preferably, the time of the magnetization roasting in step (2) is 0.5-2 h. For example, it can be 0.5 h, 0.8 h, 1.1 h, 1.4 h, 1.7 h or 2 h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the magnetic separation in step (2) includes at least one rough selection and two fine selections.

[0037] Preferably, the magnetic field intensity for rough selection is 120 - 150 mT. For example, it can be 120 mT, 130 mT, 140 mT, or 150 mT. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0038] Preferably, the magnetic field intensity for fine selection is 80 - 120 mT. For example, it can be 80 mT, 90 mT, 100 mT, 110 mT, or 120 mT. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0039] In the present invention, iron concentrate and tailings can be separated by magnetic separation. During the primary selection process, the recovery rate of iron is ensured under the condition of high magnetic intensity. The obtained magnetic separation concentrate is ground again, so that magnetite and impurities are separated again. The secondary fine selection can be carried out under the condition of low magnetic intensity to obtain magnetic separation iron concentrate with a higher grade. The magnetic separation tailings can be combined with the tailings of the first rough selection. In this way, at least two fine selections are required to obtain iron concentrate powder with a purity of 70%. The rare earth in the magnetic separation tailings is enriched to 8 - 10%, scandium oxide is enriched to more than 500 ppm, and niobium oxide is enriched to more than 0.3%.

[0040] Furthermore, the magnetic field intensity for rough selection in magnetic separation is 120 - 150 mT, and the magnetic field intensity for fine selection in magnetic separation is 80 - 120 mT. If the magnetic field intensity is too high, it will cause too high impurity content in the concentrate, affecting the product grade. If it is too low, it will cause some Fe-containing minerals not to be recovered, affecting the product yield.

[0041] As a preferred technical solution of the present invention, the process further includes finely grinding and magnetic separating the magnetic separation rough concentrate obtained in step (2) to obtain iron concentrate.

[0042] As a preferred technical solution of the present invention, the pickling in step (3) includes multi-stage countercurrent pickling;

[0043] Preferably, the multi-stage countercurrent pickling includes at least three-stage countercurrent pickling.

[0044] Preferably, the temperature of the pickling in step (4) is 40 - 80 °C. For example, it can be 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 65 °C, 70 °C, 75 °C, or 80 °C. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0045] Preferably, the time of the pickling in step (4) is 15 - 40 min. For example, it can be 15 min, 20 min, 25 min, 30 min, 35 min, or 40 min. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0046] Preferably, in the pickling in step (4), the volume ratio of the acid solution to the magnetic separation coarse tailings and the magnetic separation fine tailings is (4-10):1. For example, it can be 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0047] Preferably, the acid solution used in the pickling in step (4) includes sulfuric acid.

[0048] Preferably, the concentration of the sulfuric acid is 0.1-1 mol / L. For example, it can be 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.6 mol / L, 0.8 mol / L or 1 mol / L, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0049] It should be noted that the multi-stage countercurrent pickling in the present invention is to wash the magnetic separation tailings of the next stage with the pickling solution of the upper stage, so that rare earths are enriched in the pickling solution. The pickling process is mainly that CeOF in the tailings reacts in dilute acid to obtain soluble rare earth salts. The pickling solution can be used to pickle the magnetic separation tailings of the next stage again, reducing acid consumption and enriching rare earths in the pickling solution. In the enriched acid solution, a pickling solution enriched with rare earths and a pickling residue enriched with scandium and niobium are obtained;

[0050] Furthermore, if the concentration of the acid solution in the pickling is too high or the usage amount is too large, a large amount of impurity elements such as Al and Mg in the tailings will enter the leaching solution; on the contrary, if the concentration is too low or the usage amount is too small, the rare earth elements cannot be effectively recovered.

[0051] As a preferred technical solution of the present invention, the process further includes subjecting the pickling solution obtained in step (4) to precipitation treatment to obtain a REO product.

[0052] It should be noted that rare earths are enriched in the pickling solution of the present invention. After simple precipitation treatment, adding oxalic acid for precipitation and roasting can obtain a REO product. The REO product includes CeO2, La2O3, and Nd2O3.

[0053] As a preferred technical solution of the present invention, the temperature of the pressure acid leaching in step (5) is 200-250 °C. For example, it can be 200 °C, 210 °C, 220 °C, 230 °C, 240 °C or 250 °C, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0054] It should be noted that the purpose of the pressure acid leaching in the present invention is to strengthen the leaching of scandium-containing and niobium-containing minerals, so that niobium and scandium enter the solution in ionic form; the temperature of the pressure acid leaching is 200-250 °C. If the temperature is too high, it will lead to an increase in energy consumption, and if the temperature is too low, the leaching rate of niobium and scandium will be insufficient.

[0055] Preferably, the time of the pressure acid leaching in step (5) is 0.5-2 h. For example, it can be 0.5 h, 0.8 h, 1.1 h, 1.4 h, 1.7 h or 2 h, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0056] Preferably, the pressure of the pressure acid leaching in step (5) is 0.5-2 MPa. For example, it can be 0.5 MPa, 1 MPa, 1.5 MPa or 2 MPa, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0057] Preferably, the acid solution used in the pressure acid leaching in step (5) includes sulfuric acid.

[0058] Preferably, the concentration of the sulfuric acid is 1-4 mol / L. For example, it can be 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L or 4 mol / L, but it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0059] It should be noted that the concentration of the acid solution in the pressure acid leaching process of the present invention is 1-4 mol / L. If the concentration is too high, it will lead to an increase in acid consumption, and if the concentration is too low, the leaching rate of niobium and scandium will be insufficient. In addition, besides the leaching solution rich in scandium and niobium obtained after the pressure acid leaching of the present invention, silica slag will also be obtained.

[0060] Moreover, the scandium in the lean-selected tailings of the present invention mainly exists in aegerine, aegirine-augite, monazite and columbite. Among them, aegerine and aegirine-augite belong to single-chain silicate minerals, monazite belongs to phosphate minerals, and aegerine, aegirine-augite and columbite are all difficult to decompose, especially aegirine-augite. Therefore, pressure is required to strengthen the leaching process so that the leaching rates of niobium and scandium are both above 95%.

[0061] As a preferred technical solution of the present invention, the combined beneficiation and smelting comprehensive utilization process for lean-selected tailings provided by the present invention includes the following steps:

[0062] (1) Grind the lean-selected tailings to a particle size of more than 95 wt% of -200 mesh, and then perform at least one rough selection and three fine selections with flotation reagents to obtain fluorite rough concentrate and flotation tailings;

[0063] Among them, the content of sodium oleate in the flotation reagent is 200 - 600 g / t, the content of sodium metasilicate is 400 - 800 g / t, the content of sodium carbonate is 200 - 700 g / t, and the content of dextrin is 200 - 700 g / t;

[0064] And the rough concentrate of fluorite is refined to obtain fluorite products;

[0065] (2) The mixed reducing agent and the flotation tailings obtained in step (1) are subjected to magnetization roasting at a temperature of 500 - 800 °C for 0.5 - 2 h, and then at least one rough selection and two fine selections of magnetic separation are carried out to obtain magnetic rough concentrate and magnetic rough tailings;

[0066] Among them, the addition amount of the reducing agent is 0.5 - 2.5% of the mass of the flotation tailings; the magnetic field intensity of the rough selection is 120 - 150 mT, and the magnetic field intensity of the rough selection is 120 - 150 mT;

[0067] (3) The magnetic rough concentrate obtained in step (2) is successively finely ground and then subjected to magnetic separation to obtain magnetic iron concentrate products and magnetic separation fine tailings; the magnetic separation includes at least one rough selection and two fine selections carried out continuously;

[0068] Among them, the magnetic field intensity of the rough selection is 120 - 150 mT, and the magnetic field intensity of the rough selection is 120 - 150 mT;

[0069] (4) The magnetic rough tailings obtained in step (2) and the magnetic separation fine tailings obtained in step (3) are mixed, and then at 40 - 80 °C, at least three - stage counter - current pickling is carried out with sulfuric acid with a concentration of 0.1 - 1 mol / L for 15 - 40 min. After solid - liquid separation, pickling liquor and pickling slag are obtained;

[0070] Among them, the volume ratio of the acid liquor to the magnetic rough tailings and the magnetic separation fine tailings in the pickling is (4 - 10):1;

[0071] And the pickling liquor is subjected to precipitation treatment to obtain REO products;

[0072] (5) At 200 - 250 °C, the pickling slag obtained in step (4) is subjected to pressure acid leaching with 1 - 4 mol / L sulfuric acid for 0.5 - 2 h, and then solid - liquid separation and extraction are carried out to obtain scandium oxide and niobium oxide.

[0073] The numerical ranges described in the present invention not only include the point values listed above, but also include any point values between the above - mentioned numerical ranges not listed. Due to space limitations and for the sake of simplicity, the present invention does not exhaustively list the specific point values included in the ranges.

[0074] Compared with the prior art, the present invention has the following beneficial effects:

[0075] (1) The present invention adopts a grinding - flotation process, which improves the monomer dissociation degree of fluorite, exposes new mineral surfaces, and reduces the influence of flotation reagent pollution on fluorite flotation;

[0076] (2) Through the flotation process, the present invention recovers the valuable element F in the dilute - selected tailings, reduces the tailing discharge amount of the dilute - selected tailings, and enriches Fe and niobium - scandium in the tailings;

[0077] (3) By adopting a magnetization roasting - magnetic separation process, the present invention recovers the valuable element Fe in the tailings. Since the iron - containing minerals are acid - consuming minerals, the acid consumption in subsequent reactions and the impurity content in the acid - leaching solution are reduced. Moreover, the magnetization roasting - magnetic separation process further reduces the tailing discharge amount of the dilute - selected tailings, enables niobium - scandium to be further enriched in the tailings, decomposes bastnaesite into CeOF which is easy to react, and obtains an iron concentrate product;

[0078] (4) The process provided by the present invention can enrich scandium oxide to more than 490 ppm and niobium oxide to more than 0.6%. The introduction of pressure acid leaching makes the leaching rates of scandium and niobium both above 95%, and the niobium - scandium resources are effectively recovered and utilized. Brief Description of the Drawings

[0079] Figure 1 is the flow chart of the combined comprehensive utilization process of the dilute - selected tailings provided in Embodiment 1 of the present invention. Detailed Embodiments

[0080] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0081] The sources of some components in the following embodiments and comparative examples are as described below:

[0082] To show the treatment effect of the method described in the present invention, the dilute - selected tailings processed in the specific embodiments of the present invention are the same dilute - selected tailings. The dilute - selected tailings are taken from the dilute - selected tailings in the Bayan Obo area. After detection, the F grade in the dilute - selected tailings is 26.8%, the proportion of hematite is 11.8%, the proportion of bastnaesite is 5.0%, and the proportion of aegirine and aegirine - augite is 15.5%. Among them, the proportion of F is 17.5%, the iron oxide content is 20.4%, the total rare - earth content is 2.7%, the niobium oxide content is 0.34%, and the scandium oxide content is 240 ppm. The specific composition is shown in Table 1.

[0083] Table 1

[0084]

[0085] Embodiment 1

[0086] This embodiment provides a comprehensive utilization process for beneficiation and smelting of lean-selected tailings, as follows Figure 1 shown. The process includes the following steps:

[0087] (1) Grind 500 g of lean-selected tailings to a particle size of -200 mesh accounting for 95 wt%, and then conduct one rough selection and three fine selections using flotation reagents to obtain fluorite rough concentrate and 227 g of flotation tailings;

[0088] Among them, the content of sodium oleate in the flotation reagent is 300 g / t, the content of sodium metasilicate is 600 g / t, the content of sodium carbonate is 400 g / t, and the content of dextrin is 375 g / t; and refine the fluorite rough concentrate to obtain fluorite products;

[0089] Through the grinding-flotation treatment process, the iron, scandium, and niobium resources in the lean-selected tailings are enriched, from 20.40 wt%, 0.34 wt%, and 240 ppm to 35.18 wt%, 0.53 wt%, and 355 ppm respectively; the F content in the fluorite flotation rough concentrate is increased from 17.5% to 26.4%, and the recovery rate is above 86.5%, achieving the grinding-flotation effect, recovering the F resources in the tailings, and further enriching the iron, rare earth, and niobium-scandium resources in the tailings after flotation;

[0090] (2) Mix the reducing agent graphite powder and the 227 g of flotation tailings obtained in step (1) and conduct magnetization roasting at 700 °C in an inert gas environment for 1 h. After cooling to room temperature, conduct magnetic separation with one rough selection at a magnetic field intensity of 140 mT and two fine selections at a magnetic field intensity of 80 mT to obtain magnetic separation rough concentrate with an iron oxide content of more than 72 wt% and magnetic separation rough tailings with a total rare earth content of 9.07 wt%;

[0091] Among them, the addition amount of the reducing agent is 2% of the mass of the flotation tailings;

[0092] The content of niobium oxide in the magnetic separation rough tailings is 0.69 wt%, and the content of scandium oxide is 490 ppm; the rare earth and niobium-scandium resources are further enriched in the magnetic separation tailings, and the tailings volume is reduced by 1 / 3;

[0093] At this time, rare earths mainly exist in bastnaesite and CeOF, both of which are easily decomposed in dilute acid, and scandium mainly exists in silicate minerals and columbite;

[0094] (3) Conduct fine grinding and magnetic separation on the magnetic separation rough concentrate obtained in step (2) in sequence to obtain magnetic separation iron concentrate products and magnetic separation fine tailings; the magnetic separation includes one rough selection and two fine selections conducted continuously;

[0095] Among them, the magnetic field intensity of the rough selection is 140 mT, and the magnetic field intensity of the fine selection is 80 mT;

[0096] (4) Mix the rough tailings obtained from magnetic separation in step (2) and the fine tailings obtained from magnetic separation in step (3), and then at 40 °C, perform three-stage countercurrent pickling with sulfuric acid at a concentration of 0.5 mol / L for 20 min. After solid-liquid separation, pickling solution with a total rare earth content of 75% and pickling slag are obtained;

[0097] Among them, the volume ratio of the pickling solution, the rough tailings obtained from magnetic separation, and the fine tailings obtained from magnetic separation in the pickling is 5:1;

[0098] And perform precipitation treatment on the pickling solution to obtain REO products;

[0099] (5) At 200 °C, use sulfuric acid at a concentration of 4 mol / L to perform pressure acid leaching on the pickling slag obtained in step (4) for 1.5 h, and then perform solid-liquid separation and extraction to obtain scandium oxide and niobium oxide;

[0100] Among them, the liquid-solid ratio of sulfuric acid to the pickling slag is 5:1, and the enrichment amounts of scandium and niobium in the acid leaching solution obtained by pressure acid leaching reach 96.3% and 97.2% respectively.

[0101] Example 2

[0102] This example provides a combined beneficiation and comprehensive utilization process for rare earth separation tailings. The process includes the following steps:

[0103] (1) Grind 500 g of rare earth separation tailings to a particle size of -200 mesh accounting for 97 wt%, and then perform one rough selection and three fine selections using flotation reagents to obtain fluorite rough concentrate and flotation tailings;

[0104] Among them, the content of sodium oleate in the flotation reagent is 200 g / t, the content of sodium metasilicate is 800 g / t, the content of sodium carbonate is 200 g / t, and the content of dextrin is 200 g / t;

[0105] And refine the fluorite rough concentrate to obtain fluorite products;

[0106] (2) Mix the reducing agent and the flotation tailings obtained in step (1) and perform magnetization roasting at 500 °C for 2 h, and then perform magnetic separation with one rough selection and two fine selections to obtain magnetic separation rough concentrate and magnetic separation rough tailings;

[0107] Among them, the addition amount of the reducing agent is 0.5% of the mass of the flotation tailings; the magnetic field intensity of the rough selection is 130 mT, and the magnetic field intensity of the fine selection is 100 mT;

[0108] (3) Grind the magnetic separation rough concentrate obtained in step (2) and then perform magnetic separation to obtain magnetic separation iron concentrate products and magnetic separation fine tailings; the magnetic separation includes at least one continuous rough selection and two fine selections;

[0109] Among them, the magnetic field strength for rough selection is 130 mT, and the magnetic field strength for fine selection is 100 mT;

[0110] (4) Mix the rough tailings from magnetic separation obtained in step (2) and the fine tailings from magnetic separation obtained in step (3), and then at 60 °C, carry out three-stage countercurrent pickling with sulfuric acid at a concentration of 0.1 mol / L for 40 min. After solid-liquid separation, pickling solution and pickling slag are obtained;

[0111] Among them, the volume ratio of the pickling solution to the rough tailings from magnetic separation and the fine tailings from magnetic separation in the pickling is 10:1;

[0112] And carry out precipitation treatment on the pickling solution to obtain REO products;

[0113] (5) At 225 °C, use 2.5 mol / L sulfuric acid to carry out pressure acid leaching on the pickling slag obtained in step (4) for 1.2 h, and then carry out solid-liquid separation. The enrichment amounts of scandium and niobium in the acid leaching solution obtained by pressure acid leaching reach 97.3% and 97.8% respectively.

[0114] Example 3

[0115] This example provides a combined beneficiation and comprehensive utilization process for lean ore tailings. The process includes the following steps:

[0116] (1) Grind 500 g of lean ore tailings to a particle size of more than 95 wt% -200 mesh, and then use flotation reagents for at least one rough selection and three fine selections to obtain fluorite rough concentrate and flotation tailings;

[0117] Among them, the content of sodium oleate in the flotation reagent is 600 g / t, the content of sodium metasilicate is 400 g / t, the content of sodium carbonate is 700 g / t, and the content of dextrin is 700 g / t;

[0118] And refine the fluorite rough concentrate to obtain fluorite products;

[0119] (2) Mix the reducing agent and the flotation tailings obtained in step (1) and carry out magnetization roasting at 800 °C for 0.5 h, and then carry out magnetic separation with one rough selection and two fine selections to obtain magnetic rough concentrate and magnetic rough tailings;

[0120] Among them, the addition amount of the reducing agent is 2.5% of the mass of the flotation tailings; the magnetic field strength for rough selection is 150 mT, and the magnetic field strength for fine selection is 120 mT;

[0121] (3) Carry out fine grinding and magnetic separation on the magnetic rough concentrate obtained in step (2) in sequence to obtain magnetic iron concentrate products and magnetic fine tailings; the magnetic separation includes at least one continuous rough selection and two fine selections;

[0122] Among them, the magnetic field strength for rough selection is 150 mT, and the magnetic field strength for fine selection is 120 mT;

[0123] (4) Mix the rough tailings obtained from magnetic separation in step (2) and the fine tailings obtained from magnetic separation in step (3), and then perform three-stage countercurrent pickling with sulfuric acid at a concentration of 1 mol / L for 15 min at 80 °C. After solid-liquid separation, pickling solution and pickling residue are obtained;

[0124] Among them, the volume ratio of the pickling solution to the magnetic separation tailings in the pickling is 4:1;

[0125] And perform precipitation treatment on the pickling solution to obtain REO products;

[0126] (5) At 250 °C, use 1 mol / L sulfuric acid to perform pressure acid leaching on the pickling residue obtained in step (4) for 2 h, and then perform solid-liquid separation. The enrichment amounts of scandium and niobium in the acid leaching solution obtained by pressure acid leaching reach 97.8% and 98.2% respectively.

[0127] Example 4

[0128] This example provides a combined beneficiation and comprehensive utilization process for lean ore tailings. The difference between this process and that of Example 1 is only that:

[0129] This example omits the sodium metasilicate inhibitor in the flotation reagents in step (1).

[0130] Example 5

[0131] This example provides a combined beneficiation and comprehensive utilization process for lean ore tailings. The difference between this process and that of Example 1 is only that:

[0132] This example omits the dextrin inhibitor in the flotation reagents in step (1).

[0133] Example 6

[0134] This example provides a combined beneficiation and comprehensive utilization process for lean ore tailings. The difference between this process and that of Example 1 is only that:

[0135] This example adjusts the temperature of the magnetization roasting in step (2) to 400 °C.

[0136] Example 7

[0137] This example provides a combined beneficiation and comprehensive utilization process for lean ore tailings. The difference between this process and that of Example 1 is only that:

[0138] This example adjusts the temperature of the magnetization roasting in step (2) to 900 °C.

[0139] Example 8

[0140] This embodiment provides a combined beneficiation and metallurgy comprehensive utilization process for lean tailings. The difference between this process and that of Embodiment 1 is only that:

[0141] In this embodiment, the magnetization intensity of the concentrate in the magnetic separation in step (2) is adjusted to 60 mT, and the magnetization intensity of the rough concentrate is adjusted to 100 mT.

[0142] Embodiment 9

[0143] This embodiment provides a combined beneficiation and metallurgy comprehensive utilization process for lean tailings. The difference between this process and that of Embodiment 1 is only that:

[0144] In this embodiment, the magnetization intensity of the rough concentrate in the magnetic separation in step (2) is adjusted to 160 mT, and the magnetization intensity of the concentrate is adjusted to 130 mT.

[0145] Embodiment 10

[0146] This embodiment provides a combined beneficiation and metallurgy comprehensive utilization process for lean tailings. The difference between this process and that of Embodiment 1 is only that:

[0147] In this embodiment, the concentration of sulfuric acid in the pickling in step (4) is adjusted to 2 mol / L.

[0148] Embodiment 11

[0149] This embodiment provides a combined beneficiation and metallurgy comprehensive utilization process for lean tailings. The difference between this process and that of Embodiment 1 is only that:

[0150] In this embodiment, the concentration of sulfuric acid in the pressure acid leaching in step (5) is adjusted to 0.5 mol / L.

[0151] Embodiment 12

[0152] This embodiment provides a combined beneficiation and metallurgy comprehensive utilization process for lean tailings. The difference between this process and that of Embodiment 1 is only that:

[0153] In this embodiment, the concentration of sulfuric acid in the pressure acid leaching in step (5) is adjusted to 4.5 mol / L.

[0154] Embodiment 13

[0155] This embodiment provides a combined beneficiation and metallurgy comprehensive utilization process for lean tailings. The difference between this process and that of Embodiment 1 is only that:

[0156] In this embodiment, the temperature of the pressure acid leaching in step (5) is adjusted to 180 °C.

[0157] Embodiment 14

[0158] This embodiment provides a combined beneficiation and metallurgy comprehensive utilization process for lean tailings. The difference between this process and that of Embodiment 1 is only that:

[0159] In this embodiment, the temperature of the pressure acid leaching described in step (5) is adjusted to 280 °C.

[0160] Comparative Example 1

[0161] This comparative example provides a combined beneficiation and metallurgy comprehensive utilization process for lean selected tailings. The difference between this process and that of Example 1 is only that:

[0162] This comparative example omits the grinding process described in step (1).

[0163] Comparative Example 2

[0164] This comparative example provides a combined beneficiation and metallurgy comprehensive utilization process for lean selected tailings. The difference between this process and that of Example 1 is only that:

[0165] This comparative example omits the pickling process described in step (4), that is, directly performs pressure acid leaching on the magnetic separation tailings obtained in step (2).

[0166] Calculate the recovery rates of fluorite, iron concentrate, REO, and scandium-niobium leaching solution (obtaining scandium oxide and niobium oxide after extraction) that can be recovered by using the methods provided in the above examples and comparative examples. The results are shown in Table 2.

[0167] Table 2

[0168]

[0169]

[0170] It can be seen from Table 2 that:

[0171] (1) Through comprehensive analysis of Examples 1-3, it can be known that the process method provided by the present invention obtains crude fluorite, iron concentrate, rare earth leaching solution, and niobium-scandium leaching solution through the combined process of flotation-magnetic roasting-magnetic separation-pickling-pressure acid leaching, greatly improving the comprehensive utilization rate of tailings, reducing the discharge of tailings, reducing the acid consumption for tailings treatment, reducing the environmental pressure, and enhancing the benefits of the enterprise;

[0172] (2) Through comprehensive analysis of Example 1 and Examples 4-5, it can be known that the inhibitors in the flotation reagents need to be used in combination. Omitting any one of them will result in the ineffective separation of fluorite and iron-containing minerals, and the increase in the impurity content in the fluorite concentrate;

[0173] (3) Through comprehensive analysis of Example 1 and Examples 6-7, it can be known that the temperature of magnetic roasting will affect the conversion rate of hematite to magnetite; if the temperature is too high, it will cause over-magnetization of magnetite, and part of the magnetite is magnetized to FeO (such as Example 7); if the temperature is too low, it will cause part of the hematite to fail to be converted into magnetite (such as Example 6);

[0174] (4) By comprehensively analyzing Examples 1 and 8 - 9, it can be seen that the magnetization intensity of magnetic separation affects the process of magnetic separation of magnetic substances; if the magnetization intensity is too high, weakly magnetic impurity minerals will enter the magnetic separation concentrate, resulting in a high recovery rate but a low grade (such as Example 9); if the magnetization intensity is too low, only strongly magnetic iron-containing minerals will be magnetically separated into the magnetic separation concentrate, causing some weakly magnetic iron-containing minerals to enter the tailings and reducing the recovery rate (such as Example 8).

[0175] (5) By comprehensively analyzing Examples 1 and 10 - 14, it can be seen that the concentration of the acid solution in both pickling and pressure acid leaching affects the leaching rate of the target element; by comprehensively analyzing Examples 1 and 10 - 12, it can be seen that although increasing the acid concentration in pressure acid leaching can increase the leaching rate of the target mineral, the increase is limited and the cost is increased.

[0176] By comprehensively analyzing Examples 1 and 13 - 14, it can be seen that a relatively high temperature during the pressure acid leaching process will lead to an increase in the leaching rate of niobium and scandium. However, if the temperature continues to increase beyond 250 °C, the increase in the leaching rate is small, and the energy consumption increases significantly. If the temperature is too low, the niobium- and scandium-containing minerals cannot be effectively decomposed, so the niobium and scandium elements cannot be acid-dissolved into the solution, resulting in a low leaching rate of niobium and scandium.

[0177] (6) By comprehensively analyzing Example 1 and Comparative Example 1, it can be seen that grinding is a basic condition of the process described in the present invention, which effectively reduces the adhesion between various minerals, improves the recovery rate of the target mineral, and reduces the particle size of the minerals, thereby improving the reaction efficiency of the minerals and increasing the recovery rate of valuable elements in the minerals.

[0178] (7) By comprehensively analyzing Example 1 and Comparative Example 2, it can be seen that omitting the pickling process will cause rare earth elements to react with SO4 2- and Na + during the pressure acid leaching process, resulting in the precipitation of rare earth bisulfate double salts, reducing the recovery rate of rare earths, and a large amount of rare earth elements entering the leaching solution of pressure leaching, affecting the recovery of niobium and scandium resources.

[0179] In summary, by adopting the combined process of flotation - magnetization roasting - magnetic separation - pickling - pressure acid leaching, the present invention obtains crude fluorite ore, iron concentrate, rare earth leaching solution, and niobium and scandium leaching solution, greatly improving the comprehensive utilization rate of tailings, reducing the discharge of tailings, reducing the acid consumption for tailings treatment, reducing the environmental pressure, and enhancing the benefits of the enterprise.

[0180] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A process for the comprehensive utilization of rare earth tailings, characterized in that: The process comprises the following steps: (1) grinding and flotation treatment of the rare-separation tailings to obtain fluorite coarse concentrate and flotation tailings; (2) mixing the reducing agent and the flotation tailings obtained in step (1) to subject to magnetic roasting and magnetic separation to obtain a magnetically separated coarse concentrate and a magnetically separated coarse tailings; (3) finely grinding and magnetically separating the coarse magnetic separation concentrate obtained in step (2) to obtain a magnetic separation iron ore concentrate product and a magnetic separation concentrate tailings; (4) mixing the coarse magnetic tailings obtained in step (2) and the fine magnetic tailings obtained in step (3), and then sequentially performing pickling and solid-liquid separation to obtain pickling liquid and pickling residue; (5) subjecting the pickled slag obtained in step (4) to pressurized acid leaching, followed by solid-liquid separation and extraction to obtain scandium oxide and niobium oxide.

2. The process for combined comprehensive utilization of rare earth tailings by dressing and smelting according to claim 1, characterized in that: The end point of the grinding in step (1) is: the particle size of the rare tailings is -200 mesh accounting for more than 95wt%; Preferably, the flotation treatment includes at least one roughing process and three cleaning processes; Preferably, the process further comprises refining the fluorite crude concentrate in step (1) to obtain a fluorite product.

3. The process for combined comprehensive utilization of rare earth tailings by dressing and smelting according to claim 1 or 2, characterized in that: The flotation reagents used in the flotation treatment include sodium oleate and an inhibitor; Preferably, the inhibitor comprises sodium metasilicate, sodium carbonate and dextrin; Preferably, the content of sodium oleate in the flotation reagent is 200-600 g / t; Preferably, the content of sodium metasilicate in the flotation reagent is 400-800 g / t; Preferably, the content of sodium carbonate in the flotation reagent is 200-700 g / t; Preferably, the content of dextrin in the flotation agent is 200-700 g / t.

4. The process for combined comprehensive utilization of rare earth tailings according to any one of claims 1 to 3, characterized in that: The reducing agent in step (2) comprises charcoal powder and / or graphite powder; Preferably, the amount of the reducing agent added in step (2) is 0.5 to 2.5% of the mass of the flotation tailings.

5. The process for combined comprehensive utilization of rare earth tailings according to any one of claims 1 to 4, characterized in that: The temperature of the magnetization calcination in step (2) is 500-800°C; Preferably, the time of the magnetization calcination in step (2) is 0.5 to 2 hours.

6. The process for combined comprehensive utilization of rare earth tailings according to any one of claims 1 to 5, characterized in that: The magnetic separation in steps (2) and (3) includes at least one roughing separation and two fine separations which are carried out continuously; Preferably, the magnetic field strength of the rough selection is 120-150 mT; Preferably, the selected magnetic field strength is 80-120 mT.

7. The process for combined comprehensive utilization of rare earth tailings according to any one of claims 1 to 6, characterized in that: The pickling in step (4) includes multi-stage countercurrent pickling; Preferably, the multi-stage countercurrent pickling comprises at least three stages of countercurrent pickling; Preferably, the pickling temperature in step (4) is 40 to 80°C; Preferably, the pickling time in step (4) is 15 to 40 minutes; Preferably, in the pickling step (4), the volume ratio of the acid solution and the coarse magnetic separation tailings to the fine magnetic separation tailings is (4-10):1; Preferably, the acid solution used in the pickling in step (4) includes sulfuric acid; Preferably, the concentration of the sulfuric acid is 0.1-1 mol / L.

8. The process for combined comprehensive utilization of rare earth tailings according to any one of claims 1 to 7, characterized in that: The process further comprises subjecting the pickling solution obtained in step (4) to precipitation treatment to obtain a REO product.

9. The process for combined comprehensive utilization of rare earth tailings according to any one of claims 1 to 8, characterized in that: The temperature of the pressurized acid leaching in step (5) is 200-250° C. Preferably, the time of the pressurized acid leaching in step (5) is 0.5 to 2 hours; Preferably, the pressure of the pressurized acid leaching in step (5) is 0.5 to 2 MPa; Preferably, the pressurized acid leaching in step (5) uses an acid solution including sulfuric acid; Preferably, the concentration of the sulfuric acid is 1-4 mol / L.

10. The process for combined comprehensive utilization of rare earth tailings according to any one of claims 1 to 9, characterized in that: The process comprises the following steps: (1) grinding the rare tailings to a particle size of -200 mesh accounting for more than 95 wt%, and then using a flotation agent for at least one roughing and three fine cleaning to obtain a fluorite rough concentrate and flotation tailings; The content of sodium oleate in the flotation reagent is 200-600 g / t, the content of sodium metasilicate is 400-800 g / t, the content of sodium carbonate is 200-700 g / t, and the content of dextrin is 200-700 g / t. and refining the fluorite crude concentrate to obtain a fluorite product; (2) the mixed reducing agent and the flotation tailings obtained in step (1) are subjected to magnetic roasting at a temperature of 500 to 800° C. for 0.5 to 2 h, and then subjected to at least one roughing separation and two fine separations to obtain a magnetically separated rough concentrate and a magnetically separated rough tailings; The amount of the reducing agent added is 0.5-2.5% of the mass of the flotation tailings; the magnetic field strength of the roughing is 120-150 mT, and the magnetic field strength of the fine selection is 80-120 mT; (3) fine grinding and magnetic separation are performed on the magnetically separated rough concentrate obtained in step (2) to obtain a magnetically separated iron ore concentrate product and a magnetically separated concentrated tailings; the magnetic separation includes at least one continuous roughing separation and two continuous fine separations; Wherein, the magnetic field strength of the rough selection is 120-150 mT, and the magnetic field strength of the fine selection is 80-120 mT; The magnetically separated coarse concentrate is then finely ground and magnetically separated to obtain an iron concentrate; (4) mixing the coarse magnetic tailings obtained in step (2) and the fine magnetic tailings obtained in step (3), and then performing at least three-stage countercurrent pickling at 40 to 80° C. for 15 to 40 minutes using sulfuric acid with a concentration of 0.1 to 1 mol / L, and obtaining a pickling solution and pickling residue after solid-liquid separation; The volume ratio of the acid solution to the coarse magnetic tailings and the fine magnetic tailings used in the pickling is (4-10):1; and subjecting the pickling liquid to precipitation treatment to obtain REO product; (5) The pickling residue obtained in step (4) is subjected to pressure acid leaching at 200 to 250° C. using 1 to 4 mol / L sulfuric acid for 0.5 to 2 h, followed by solid-liquid separation and extraction to obtain scandium oxide and niobium oxide.

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