Method for stepwise recovery of valuable components from sulphur-containing iron tailings

Abstract

The application discloses a method for gradient recycling of valuable components in sulfur-containing iron tailings, and the sulfur-containing iron tailings are subjected to heavy dressing by a shaking table to obtain a sulfur concentrate, the low-sulfur iron tailings 1 discharged is subjected to screening to obtain coarse-grained iron tailings on the screen, fine-grained iron tailings discharged on the screen is subjected to sulfuric acid dissolution on Fe, excessive ammonia water is added into leaching liquor 1 to react and solid-liquid separation is conducted, Fe(OH)3 solid is obtained, evaporation crystallization is conducted on leaching liquor 2 to obtain an ammonium salt, auxiliary materials are added into leaching residue, wet grinding, uniform mixing, pressing and sintering are conducted to obtain building ceramic products with different purposes, and full utilization of the leaching residue is finally realized. The method is conducted under normal temperature and pressure, has simple processing technology and low cost, does not introduce other secondary pollution in the whole process, and realizes full utilization of valuable components in the sulfur-containing iron tailings, has a good application prospect in the field of comprehensive utilization of the sulfur-containing iron tailings, and is suitable for industrialized popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive utilization of solid waste resources in mining, specifically involving the recycling of valuable components in sulfur-containing iron tailings. It is particularly suitable for the tiered recycling of valuable components in iron tailings with SO3 content ≥2%, promoting the large-scale reduction and full utilization of iron tailings resources in mining areas. Background Technology

[0002] Mineral resources, as a fundamental guarantee for human survival and development, hold a vital strategic position. With the continuous development and utilization of mineral resources, easily processed single ores are gradually decreasing, and the characteristics of mineral resources being "poor, fine, and complex" are becoming increasingly prominent. A large amount of iron tailings needs to be imported annually; however, the iron oxide content in the iron tailings produced each year can reach 10-20%. Based on the current annual production of approximately 600 million tons of iron tailings, tens of millions of tons of iron are not being fully utilized, including the recovery and utilization of sulfur components. Effectively reusing the valuable components in iron tailings would greatly promote the reduction of iron tailings volume, efficient resource utilization, and the secure supply of iron and other resources.

[0003] The large-scale stockpiling of iron tailings not only occupies land resources and damages the environment, but also poses certain safety hazards. Therefore, fully and rationally recovering valuable components such as Fe2O3 from iron tailings and using its leaching residue to prepare building materials, effectively realizing the tiered and full-scale utilization of iron tailings, and achieving the reduction, harmlessness, and resource utilization of iron tailings, has significant and far-reaching environmental, social, and economic implications.

[0004] To address the aforementioned issues, extensive research and exploration have been conducted both domestically and internationally on the treatment and application of iron tailings. Regarding the recovery of valuable components, the literature "Deep Recovery Process of Iron Tailings by Magnetizing Roasting-Magnetic Separation" addresses the problems of easy mud formation, severe entrainment, and low iron grade recovery by conventional magnetic separation and flotation methods in a certain iron tailings. It employs a beneficiation process of strong magnetic tailings removal—magnetizing roasting—weak magnetic roughing—fine grinding—weak magnetic cleaning. After magnetizing roasting, the entrainment phenomenon is significantly reduced, ultimately yielding an iron concentrate with a w(TFe) of 61.55%. However, the energy consumption and cost of the magnetizing roasting process are high, and its economic benefits are often insufficient to support large-scale application. To achieve large-scale disposal and utilization of tailings, patent application number 201910221447.4, "A Method for Soil Treatment of Acidic Tailings," involves firstly drying, crushing, and sieving acidic tailings and biomass waste separately for later use. Next, 0.8-1.2 parts by weight of acidic tailings and 2-5 parts by weight of biomass waste are mixed evenly. The mixture is then piled up, and the pile is ignited. After the biomass waste has fully burned and the flame extinguished, the treated mixture is thoroughly mixed with the remaining biomass waste, dried, and then placed in a carbonization furnace for carbonization to obtain acidic tailings carbon. However, this method for soil treatment of acidic tailings has a long overall pretreatment cycle and high costs, specifically including iron tailings slurry filtration before drying, combustion, and carbonization processes. Furthermore, the environmental stability of its ecological application in the later stages requires further investigation. Regarding the utilization of building materials, the literature "Mechanical Properties and Microstructure Analysis of Recycled Iron Tailings Sand Concrete" shows that when iron tailings replace 30% of natural aggregates, the concrete system achieves the optimal degree of hydration and particle packing density, significantly improving the compactness of the specimens. However, for iron tailings with high associated sulfur content, their application cannot be promoted due to the restrictions of the national standard "Construction Sand".

[0005] Furthermore, some iron ore tailings cannot be used as large-scale building materials due to their sulfur and mud content. To address the challenge of comprehensive utilization of sulfur-containing iron tailings, the paper "Experimental Study on the Recovery of Pyrite Minerals from a Tailings Mine in Western Yunnan," published in the first issue of *Comprehensive Utilization of Mineral Resources* in 2019, conducted a beneficiation study on pyrite tailings, primarily composed of pyrrhotite. Based on the experimental results, a reasonable process flow was recommended as a combined flotation-magnetic-regrinding-flotation process. This process yielded two different grades of sulfur concentrate (containing 38.21% and 29.35% sulfur), with a total sulfur recovery rate of 93.74%; the iron concentrate contained 63.88% iron and 1.66% sulfur, with an iron recovery rate of 23.29%. However, the iron concentrate obtained in this study had a high sulfur content and could not be sold as commercial iron concentrate, and it also generated 53.97% new tailings.

[0006] Therefore, based on the above situation, it is necessary to conduct systematic research and exploration on iron tailings, especially sulfur-containing iron tailings, to form a systematic treatment approach and propose a new method for the large-scale treatment and utilization of sulfur-containing iron tailings. Summary of the Invention

[0007] The purpose of this invention is to address the problems of low comprehensive utilization rate, high cost, and easy secondary pollution to the environment caused by existing iron tailings utilization technologies, and to provide a more comprehensive utilization method.

[0008] This method involves the tiered recovery of valuable components from sulfur-containing iron tailings, which is simple, low-cost, and environmentally friendly. It not only recovers sulfur and iron resources from iron tailings in a tiered manner but also achieves full utilization of leaching residue.

[0009] To achieve the above-mentioned objectives of this invention, the technical concept of the method is as follows: Considering that pyrite is often associated with iron ore, the primary focus is on the recovery of sulfur concentrate, which involves both the recovery of valuable components and the detoxification of coarse-grained iron tailings and the elimination of other unfavorable factors in utilization. Secondly, screening maximizes the utilization of the tailings for low-cost processing in building materials. Finally, focusing on fine-grained iron tailings, acid leaching is used to recover iron components and prepare ceramic materials for building applications, with ammonium salts as a byproduct for use as soil fertilizer.

[0010] This invention discloses a method for the tiered recovery and utilization of valuable components in sulfur-containing iron tailings, used to treat sulfur-containing iron tailings with SO3 content between 2% and 8%. The method is implemented through the following steps:

[0011] (1) The sulfur-containing iron tailings are subjected to gravity separation by shaking table to obtain sulfur concentrate with a sulfur grade of 34.0%-40.0%, and low-sulfur iron tailings are discharged.

[0012] (2) The low-sulfur iron tailings 1 discharged in step (1) are screened through a linear screen with a screen size of 0.15-0.30mm to obtain coarse iron tailings on the screen for sale as sand and gravel aggregate products, and fine iron tailings on the screen are discharged.

[0013] (3) The fine iron tailings discharged in step (2) are subjected to Fe dissolution under the conditions of liquid-solid ratio of 65-85 ml / g and sulfuric acid mass concentration of 2-8%. The leaching time is controlled at 15-25 min and the leaching temperature is controlled at 20-30℃. The leaching solution 1 and leaching residue are obtained by solid-liquid separation.

[0014] (4) Add excess ammonia water to the leachate 1 obtained in step (3) to react and generate flocculent precipitate Fe(OH)3; perform solid-liquid separation on the solution containing flocculent precipitate Fe(OH)3 to obtain Fe(OH)3 solid and leachate 2 respectively; calcine the Fe(OH)3 solid to obtain Fe2O3 product, which is sold as iron red product.

[0015] (5) The leachate 2 obtained in step (4) is used to obtain ammonium salt (NH4)2SO4 by evaporation crystallization.

[0016] (6) Add auxiliary materials such as silicon-aluminum raw materials and calcium-magnesium raw materials to the leaching residue obtained in step (3). According to market demand, design different addition schemes according to the requirements of ceramic raw material composition. After wet grinding and mixing, pressing and molding and sintering, architectural ceramic products with different uses are obtained, and finally the full utilization of leaching residue is realized.

[0017] Preferably, in step (1), the lateral slope of the shaking table re-selection device is 1° ~ 2°, the stroke rate is 300 ~ 400 times / min, and the stroke is 6mm ~ 9mm.

[0018] Preferably, the gangue minerals in the pyrite-containing tailings are mainly quartz and feldspar, the iron minerals are mainly magnetite, hematite, and limonite, and the sulfur mineral is pyrite; the main chemical composition of the pyrite-containing tailings is 40% by mass percentage. <SiO2<60%,10%<Al2O3<25%,8%<Fe2O3<25%,2%<SO3<8%。

[0019] Preferably, the ammonium salt (NH4)2SO4 obtained in step (5) is used as soil fertilizer for ecological restoration of mine waste sites.

[0020] Preferably, the sieve aperture size in step (2) is 0.15 mm.

[0021] Preferably, in step (3), the liquid-to-solid ratio is 70-80 ml / g, the sulfuric acid concentration is 4-8%, the leaching time is controlled at 15-20 min, and the leaching temperature is controlled at 25-29℃.

[0022] This invention uses sulfur-containing iron tailings as raw material. Through gravity separation and screening, and employing a low-temperature, low-pressure hydrochemical method, it recovers the sulfur and iron components from the iron tailings, achieving the tiered recovery and utilization of different resources within the iron tailings. Compared with existing technologies, this method for the tiered recovery and utilization of valuable components from sulfur-containing iron tailings has the following beneficial effects:

[0023] (1) The method of the present invention fully considers the mineral phase characteristics and mineral composition of sulfide-containing iron tailings, and eliminates the unfavorable factors in the utilization process. First, the sulfur component is recovered to detoxify it for subsequent use in coarse iron tailings utilization. The acid leaching recovery of the iron component realizes the reduction of iron content in the leaching residue used for ceramic material preparation, as a high iron content is not conducive to the preparation of ceramic materials. Among them, the screening and recovery of coarse iron tailings is, on the one hand, an efficient and low-cost treatment to realize the productization of this part of the iron tailings, and on the other hand, it also reduces the input of acid leaching and dissociation, and at the same time reduces the coarse particles of the leaching residue component, thus reducing the grinding energy consumption in the preparation of ceramic materials.

[0024] (2) The method of the present invention utilizes the low solubility of CaO, SiO2 and Al2O3 in dilute acid solution (mainly because these components exist in mineral phases), while the iron component can be well dissolved in acid solution (because the iron component mainly exists in the form of magnetite phase, hematite phase and limonite phase which are easily soluble in acid solution), thereby achieving efficient separation of Fe resources and other oxides in iron tailings.

[0025] (3) Compared with the application methods reported at home and abroad, such as magnetization roasting and flocculation-flotation, the method proposed in this invention is carried out under mild conditions of normal temperature and pressure, which achieves a high recovery rate of iron components, so that the final recovery rate of Fe2O3 in iron tailings reaches more than 80%.

[0026] (4) The method mentioned in this invention achieves energy saving and consumption reduction in the iron tailings recycling process, realizes the cascade recycling and utilization of various resources in the iron tailings, and improves resource utilization rate. In addition, the method of this invention has low pollution, no tail gas, and eliminates the pollution caused by sulfur carried in iron tailings to the environment. It is an iron tailings treatment process with large-scale application prospects. Attached Figure Description

[0027] Figure 1 This is a flowchart illustrating the principle and process flow of a method for the tiered recovery and utilization of valuable components in sulfur-containing iron tailings according to the present invention. Detailed Implementation

[0028] To better describe the present invention, a method for the tiered recovery and utilization of valuable components in sulfide-containing iron tailings according to the present invention will be further described in detail below with reference to the accompanying drawings. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Specific conditions and parameters not specified in the embodiments are performed according to conventional conditions or conditions recommended by on-site operators. Reagents, instruments, and equipment used, unless otherwise specified, are all commercially available products.

[0029] The sulfur-containing iron tailings used in this embodiment of the invention are tailings from the beneficiation process of a large open-pit iron mine in East China.

[0030] The main components (wt.%) of the sulfur-containing iron tailings used in the embodiments of the present invention are shown in Table 1 below.

[0031] Table 1. Main chemical components (wt.%) of pyrite tailings

[0032] content 47.65 16.68 12.57 6.50 6.45 4.24 3.59 0.24

[0033] Depend on Figure 1 The flowchart illustrating the principle of this invention's method for the tiered recovery and utilization of valuable components from sulfur-containing iron tailings shows that the technical route of this invention is as follows: shaking table gravity separation for sulfur recovery – screening of coarse iron tailings – acid leaching, ammonia precipitation for iron removal, iron resource recovery – ammonium salt recovery – full utilization of leaching residue (for building ceramic materials). The specific processing steps are as follows:

[0034] (1) A certain amount of sulfur-containing iron tailings were taken and subjected to gravity separation on a shaking table. The stroke parameters were 325, 350 and 375 times / minute, and the strokes were 8 mm, 7 mm and 6 mm, respectively. The transverse slope of the shaking table was 1.5°. The sulfur grades of the resulting sulfur concentrates were 34.55%, 39.77% and 39.98%, respectively, and the yields were 3.72%, 3.06% and 2.46%, respectively. It can be seen that as the stroke rate increases, the sulfur grade increases while the yield decreases. Considering the sulfur grade and the yield of the sulfur concentrate, the preferred stroke rate is 350 times / minute and the stroke is 7 mm. The sulfur concentrate (of which the Fe content is 32.76%) was recovered, and the low-sulfur iron tailings 1 were discharged for later use.

[0035] (2) The low-sulfur iron tailings 1 discharged in step (1) are screened through a sieve with a 0.15mm aperture. The coarse iron tailings on the sieve are used as sand and gravel aggregate, and the fine iron tailings discharged are reserved for use.

[0036] (3) Take a certain amount of undersized fine iron tailings and add it to sulfuric acid solutions with a mass percentage concentration of 4% and 6%. The liquid-solid ratio of H2SO4 to undersized fine iron tailings is 70mL / g and 80mL / g, respectively. After uniform mixing, transfer it to a three-necked flask, adjust the stirring speed, and react at room temperature (25℃) for 1 min (control group) and 20 min. After the reaction is completed, filter the slurry and separate the liquid and solid to obtain leachate 1 and leach residue, respectively.

[0037] ICP-MS analysis of leachate 1 obtained under different leaching conditions showed that: when the sulfuric acid concentration was 4%, the liquid-to-solid ratio of H2SO4 to sulfide-containing iron tailings was 70 mL / g, and the leaching time was 1 min, the Fe concentration in a 500 mL solution reached 32.6 mg / L; when the sulfuric acid concentration was 4%, the liquid-to-solid ratio of H2SO4 to sulfide-containing iron tailings was 70 mL / g, and the leaching time was 20 min, the Fe concentration in a 500 mL solution reached 32.6 mg / L. The concentration of Fe can reach 146 mg / L; when the sulfuric acid concentration is 4%, the liquid-solid ratio of H2SO4 to sulfide iron tailings is 80 mL / g, and the leaching time is 20 min, the Fe concentration in a 500 mL solution can reach 163 mg / L; when the sulfuric acid concentration is 6%, the liquid-solid ratio of H2SO4 to sulfide iron tailings is 80 mL / g, and the leaching time is 20 min, the Fe concentration in a 500 mL solution can reach 172 mg / L. These experimental data show that the Fe leaching rate can reach over 80% (excluding the Fe component from the sulfur concentrate and coarse-grained iron tailings). Increasing the liquid-solid ratio in the system can significantly increase the Fe solubility in the leachate, i.e., increase the Fe leaching rate from the original ore. When the sulfuric acid concentration is 8%, the liquid-solid ratio of H2SO4 to iron tailings is 80 mL / g, and the leaching time is 20 min, the Fe leaching rate can reach 96.09%.

[0038] (4) Transfer the leachate 1 obtained in step (3) into an Erlenmeyer flask. At this time, the leachate 1 contains a large amount of Fe. 3+ In order to remove Fe from leachate 1 3+ To convert it into a precipitate and recover it, the OH- ions in the solution need to be adjusted. - Solubility of ions. The pH meter probe was incorporated into the solution, and ammonia solution was continuously added to the conical flask. When the content of the flocculent precipitate in the conical flask no longer changed, the solution containing the flocculent precipitate Fe(OH)3 was filtered to obtain Fe(OH)3 solid and leachate 2. The Fe(OH)3 solid was calcined to obtain Fe2O3 product, which was sold as iron oxide red.

[0039] (5) The leachate 2 obtained in step (4) is heated and evaporated on an electric hot plate to crystallize and obtain ammonium salt (NH4)2SO4. Ammonium salt (NH4)2SO4 can be used as soil fertilizer for the ecological restoration of abandoned mine sites.

[0040] (6) By testing the moisture content of the leaching residue obtained in step (3), different additive ratios of silicon-aluminum raw materials and calcium-magnesium raw materials are designed. Through wet grinding and mixing, and sintering, different types of ceramic products can be obtained, such as ceramic tiles, sintered bricks, ceramsite and other building ceramic products, so as to realize the cascade full-quantity utilization of iron tailings resources.

[0041] Studies have shown that the method for the tiered recovery and utilization of valuable components in sulfur-containing iron tailings of this invention has a simple processing technology, low cost, and no introduction of other secondary pollution throughout the process. It also achieves full and complete utilization of valuable components in iron tailings, and has good application prospects in the field of comprehensive utilization of iron tailings, making it suitable for industrial promotion.

Claims

1. A method for the tiered recovery and utilization of valuable components in sulfur-containing iron tailings, characterized in that... The following steps are to be taken: (1) The pyrite-containing tailings are subjected to shaking table gravity separation to obtain a sulfur concentrate with a sulfur grade of 34.0%-40.0%, and low-sulfur pyrite tailings I are discharged; the shaking table gravity separation equipment has a transverse slope of 1°~2°, a stroke rate of 300~400 times / min, and a stroke of 6mm~9mm; the gangue minerals in the pyrite-containing tailings are mainly quartz and feldspar, the iron minerals are mainly magnetite, hematite and limonite, and the sulfur mineral is pyrite; the main chemical components of the pyrite-containing tailings are 40% by mass percentage. <SiO2<60%,10%<Al2O3<25%,8%<Fe2O3<25%,2%<SO3<8%; (2) The low-sulfur iron tailings I discharged in step (1) are screened through a linear screen with a screen size of 0.15-0.30mm to obtain coarse iron tailings sand on the screen as sand and gravel aggregate products, and fine iron tailings under the screen are discharged. (3) The fine iron tailings discharged in step (2) are subjected to Fe dissolution under the conditions of liquid-solid ratio of 65-85 ml / g and sulfuric acid mass concentration of 2-8%. The leaching time is controlled at 15-25 min and the leaching temperature is controlled at 20-30℃. The leaching solution I and leaching residue are obtained by solid-liquid separation. (4) Add excess ammonia water to the leachate I obtained in step (3) to react and generate flocculent precipitate Fe(OH)3; perform solid-liquid separation on the solution containing flocculent precipitate Fe(OH)3 to obtain Fe(OH)3 solid and leachate II respectively; calcine the Fe(OH)3 solid to obtain Fe2O3 product; (5) The leachate II obtained in step (4) is used to obtain ammonium salt (NH4)2SO4 by evaporation crystallization. (6) Add auxiliary materials such as silicon-aluminum raw materials and calcium-magnesium raw materials to the leaching residue obtained in step (3). Design different addition schemes according to the requirements of ceramic raw material composition. After wet grinding and mixing, pressing and sintering, architectural ceramic products with different uses are obtained, and finally the full utilization of leaching residue is realized.

2. The method for cascade recovery and utilization of valuable components in sulfur-containing iron tailings as described in claim 1, characterized in that: The ammonium salt (NH4)2SO4 obtained in step (5) is used as soil fertilizer for the ecological restoration of abandoned mining sites.

3. The method for cascade recovery and utilization of valuable components in sulfur-containing iron tailings as described in claim 2, characterized in that: In step (2), the sieve aperture size is 0.15 mm.

4. A method for the tiered recovery and utilization of valuable components in sulfur-containing iron tailings as described in claim 1, 2, or 3, characterized in that: In step (3), the liquid-to-solid ratio is 70-80 ml / g, the sulfuric acid concentration is 4-8%, the leaching time is controlled at 15-20 min, and the leaching temperature is controlled at 25-29℃.

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