Method for recovering calcium and iron by melting and wet separation of steel slag

Abstract

The application discloses a method for separating, enriching and recovering calcium and iron from steel slag by melting and wet method, which comprises the following steps: firstly, crushing and grinding the steel slag into powder; then, uniformly mixing the steel slag with flux according to a proportion, melting the mixture at high temperature to prepare a steel slag melting product, further crushing and grinding the steel slag melting product into powder, and mixing the powder with acid to completely dissolve the powder; then, adding alkali liquor into the solution to adjust the PH value, so that the solution is completely precipitated and filtered; and finally, cleaning, drying and grinding the filter cake obtained by filtration to prepare powder. The calcium and iron elements in the modified steel slag are enriched, and compared with the initial steel slag, the calcium oxide content of ton steel slag is increased by about 201 kg at most, and the iron oxide content of ton steel slag is increased by about 84 kg at most. The method can effectively enrich the calcium and iron elements in the steel slag, and the elements can be directly used as raw materials for blast furnace iron making in a production process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of industrial solid waste treatment and comprehensive utilization, and particularly relates to a method for smelting, wet separation, enrichment and recovery of calcium and iron from steel slag. BACKGROUND

[0002] Steel slag is a solid waste generated in the steelmaking process. China has the world's first steel production, and the amount of steel slag discharged is also the first. However, the utilization rate of steel slag in China is low. Those steel slags that cannot be fully utilized and treated occupy a large amount of land, not only wasting resources, but also polluting the environment. Steel slag contains a large amount of iron elements, with an average mass fraction of about 28%, of which about 10% of metallic iron can be collected through crushing, classification screening, magnetic separation and other processes as a raw material for steelmaking and ironmaking. The remaining steel slag with low iron content is discarded due to technical reasons or production costs, which not only seriously hinders the further application of steel slag, but also causes serious waste of iron resources.

[0003] At present, the methods for recovering metallic iron and oxides in steel slag mainly include three kinds: magnetic separation, reduction and oxidation. The magnetic separation method is widely used. The reduction method uses the reduction effect of inorganic carbon at high temperature to reduce ferrous oxide in steel slag into elemental iron, but the whole process requires high temperature and will produce greenhouse gases. The oxidation method is a process for converting non-magnetic FeO inside the steel slag into magnetic Fe3O4, which is only a new research direction and cannot be applied to industrialization at present. In addition, there are also steel slag gravity separation and flotation technologies, but due to high production cost and low profit, their application is less.

[0004] Converter steel slag contains 40% to 50% CaO, which can be recovered as a blast furnace dissolving agent to replace limestone and dolomite, thereby saving mineral resources. Secondly, it can also be used to adsorb pollutants in wastewater, remove SO2 gas in flue gas, and adsorb CO2 gas, etc. However, there are few reports on the preparation of CaO from steel slag alone at present, and generally the reports are about the separation and extraction of metal and calcium oxide combined with metal elements in steel slag. For example, Lv Yeqing et al. invented a method for enriching vanadium in vanadium-containing steel slag and preparing calcium carbonate (patent CN114293035A). The method includes mixing vanadium-containing steel slag with ammonium salt solution, placing the mixture under vacuum conditions, separating the vanadium-rich slag and calcium-rich solution, and then generating fine calcium carbonate by absorbing CO2 gas. The biggest problem of this method is that it needs to be carried out under vacuum conditions, which is difficult to operate in actual production.

[0005] How to efficiently and economically recover iron and calcium elements in steel slag has become a research hotspot. At present, more research is on wet leaching of steel slag and then separating and precipitating iron and calcium. However, in the process of leaching of steel slag, the dissolution rate is often low, and finally a part of the steel slag cannot be dissolved. In addition, the solid-liquid ratio in the process of leaching of steel slag is high, which consumes a large amount of leaching liquid and leads to the need of consuming a large amount of alkali liquid in subsequent precipitation, thereby increasing the production cost. Meanwhile, the undissolved steel slag needs to be further treated to avoid secondary pollution. In view of the above problems, the present application proposes a method combining pyrometallurgy and hydrometallurgy to separate and enrich calcium and iron in steel slag, that is, first melting the steel slag with a mixed flux to completely dissolve the steel slag, then leaching the steel slag with an acid liquid, completely dissolving the steel slag into a solution, then filtering and separating the solution after alkali leaching and precipitation, and drying the obtained filter residue to become an enrichment of calcium and iron. SUMMARY

[0006] The present application is based on the element composition characteristics of steel slag “high calcium and rich iron”, and aims at high value utilization of steel slag. Through the treatment method of mixed flux melting-acid leaching, the enrichment of calcium and iron elements is realized. This method effectively solves the technical challenges brought by the difficulty of completely separating and extracting valuable elements from steel slag solids, and realizes the high value utilization of steel slag.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme to realize it:

[0008] A method for separating and enriching and recovering calcium and iron by melting and wet method of steel slag, comprising the following steps:

[0009] 1. crushing the steel slag, and detecting and controlling the content of the components;

[0010] 2. mixing the steel slag obtained in step 1 with a fluxing agent according to a mass ratio of 1:(1-20), and then reacting at 800-1400℃ for 5-120min to completely melt, and then cooling to form a glassy phase steel slag, and then crushing and grinding the glassy phase steel slag into a powder;

[0011] 3. adding hydrochloric acid to the powder obtained in step 2 according to a mass-volume ratio of 1:(3-20)g:ml, and stirring at a reaction temperature of 180-300℃ until a mixed solution is obtained;

[0012] 4. adding hydrofluoric acid to the mixed solution obtained in step 3, and the addition amount is according to a mass-volume ratio of steel slag:hydrofluoric acid=1:(1-5)g:ml, and then heating at 90-400℃ for 20-180min, and then adding perchloric acid solution to the solution, and the addition amount is according to a mass-volume ratio of steel slag:perchloric acid solution=1:(0.5-2)g:ml, and then stirring at 90-400℃ for 20-180min, and then stopping stirring and cooling to room temperature;

[0013] 5. Add sodium hydroxide to the solution obtained in step 4, and the mass-volume ratio of the steel slag to the sodium hydroxide is 1: (0.5-3) g / ml, so that the precipitation is complete;

[0014] 6. Filter the precipitated solution obtained in step 5 to obtain a filtrate and a filter cake, and the filtrate is reserved, and the filter cake is washed with water for multiple times and then filtered again;

[0015] 7. Place the filter cake obtained in step 6 in an oven at 110°C for 10-12 hours, dry the filter cake, grind it into powder, and then detect and analyze the powder.

[0016] Further preferably, the steel slag in step 1 is converter steel slag or electric furnace steel slag.

[0017] Further preferably, the component content of the steel slag in step 1 is as follows: CaO: 20%-45%, Fe2O3: 10%-35%, SiO2: 10%-30%, Al2O3: 0.5%-9%, MgO: 2%-15%, V2O5: 0.2%-8%, TiO2: 0.2%-0.9%, SrO: 0.01%-0.08%, CuO: 0.01%-0.08%, and NbO: 0.02%-0.08%.

[0018] Further preferably, the fluxing agent in step 2 is one or a mixture of multiple kinds in any ratio of lithium tetraborate, lithium metaborate, sodium carbonate, boric acid, and sodium peroxide.

[0019] Further preferably, the particle size of the powder-like steel slag in step 2 is ≤0.2 mm.

[0020] Further preferably, the mass concentration of the hydrochloric acid in step 3 is 30%-37%.

[0021] Further preferably, the stirring speed in step 4 is 30-180 r / min.

[0022] Further preferably, the mass concentration of the sodium hydroxide in step 5 is 200-400 g / L, and the PH of the solution is controlled to be 3-4.

[0023] Further preferably, the number of times of washing with water in step 6 is ≥5.

[0024] The present application aims to enrich calcium and iron elements in steel slag by using fluxing agent and steel slag melting-acid leaching treatment method, and realize high value utilization of steel slag. Therefore, the present application proposes a method, which comprises mixing steel slag with fluxing agent, and then dissolving the obtained mixture with hydrochloric acid. The fluxing agent helps to melt the steel slag, thereby facilitating its complete dissolution in hydrochloric acid. In addition, fluorine ions can react with silicon elements to generate volatile silicon tetrafluoride, thus having special decomposition ability for silicate rocks and oxide minerals. Using hydrofluoric acid as a selective leaching agent helps to extract and separate silicon elements in the form of silicate and silicon oxide compounds in steel slag. The recovered calcium and iron can be directly used as production raw materials. After calcium and iron are separated, calcium can be used as a fluxing agent instead of limestone in blast furnaces, and also as an adsorbent material.

[0025] The present application has the advantages and beneficial effects of:

[0026] (1) Compared with existing separation technologies, the present application is based on the characteristics of steel slag, uses a method of mixing steel slag with fluxing agent and high-temperature melting to accelerate the dissolution rate of steel slag in concentrated acid solution, shorten the reaction time, and completely dissolve the steel slag. In addition, the present application also uses hydrofluoric acid solution as a selective leaching agent to further convert the silicate oxide component and achieve the purpose of separating from the steel slag. Subsequently, an alkali solution is added to precipitate and filter the solid material, achieving the effect of enriching calcium and iron elements in the material. According to the calculation, the calcium oxide in the solid material is increased by about 20.1% compared to the initial steel slag, and the iron oxide is increased by about 8.4%.

[0027] (2) The method has a simpler process flow and more convenient operation compared with traditional methods. The steel slag is completely dissolved, no secondary solid waste residue is generated, and silicon can be quickly removed. The final product is mainly calcium and iron-containing compounds. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The present application is a process flow diagram for steel slag melting-wet separation and enrichment of calcium and iron. DETAILED DESCRIPTION

[0029] The following examples further illustrate the present application, but should not be construed as limiting the present application. Modifications and substitutions to the methods, steps or conditions of the present application without departing from the spirit and essence thereof shall fall within the scope of the present application. If not specifically indicated, the technical means used in the examples are conventional means known to those skilled in the art.

[0030] Example 1

[0031] A method for steel slag melting-wet separation and enrichment of calcium and iron, comprising the following steps:

[0032] The powdered steel slag (≤0.2mm) is mixed with fluxing agent (fluxing agent 1: fluxing agent 2 = 67:33) at a ratio of 1:1 (mass ratio), and is reacted (5-120 min) at (800-1100°C) to completely melt it, and after cooling, a glassy phase steel slag sample is formed, which is then broken and ground into powder (≤0.2mm), and 36% hydrochloric acid (mass fraction) is added at a solid-liquid ratio of steel slag to hydrochloric acid (1:5.5 / g:ml), and is fully stirred at 240°C until it is completely dissolved, and 40% hydrofluoric acid is added at a solid-liquid ratio of steel slag to hydrofluoric acid (1:2 / g:ml), and after 40 minutes at a constant temperature of 240°C, perchloric acid is added at a solid-liquid ratio of steel slag to perchloric acid (1:0.7 / g:ml), and after stirring for 15 minutes, it is lowered to room temperature, and then NaOH (200g / ml) solution is added at a solid-liquid ratio of steel slag to sodium hydroxide (1:2 / g:ml), so that it starts to precipitate, and 10g of sodium hydroxide solid is continuously added to adjust the pH value to 3-4, so that it completely precipitates, and then the precipitate is filtered to obtain filtrate and filter cake, the filtrate is retained, and the filter cake is washed with water five times, and after filtration, the obtained filter cake is placed in an oven at 110°C for 10-12 hours, and after complete drying, it is ground into powder, and the chemical composition (Table 1) is detected and analyzed. As shown in Table 1, the mass fraction of CaO is 46.1%, and the mass fraction of Fe2O3 is 38.2%.

[0033] Example 2

[0034] A method for melting-wet separation and enrichment of calcium and iron from steel slag, comprising the following steps:

[0035] The powdered steel slag is mixed with fluxing agent (fluxing agent 1: fluxing agent 2 = 67:33) at a ratio of 1:20 (mass ratio), and is reacted (5-120 min) at (800-1400°C) to completely melt it, and after cooling, a glassy phase steel slag sample is formed, which is then broken and ground into powder, and concentrated hydrochloric acid is added at a solid-liquid ratio of steel slag to hydrochloric acid (1:20 / g:ml), and is fully stirred at 240°C until it is completely dissolved, and 40% hydrofluoric acid is added at a solid-liquid ratio of steel slag to hydrofluoric acid (1:5 / g:ml), and after 40 minutes at a constant temperature of 240°C, perchloric acid is added at a solid-liquid ratio of steel slag to perchloric acid (1:2 / g:ml), and after stirring for 15 minutes, it is lowered to room temperature, and then NaOH (200g / ml) solution is added at a solid-liquid ratio of steel slag to sodium hydroxide (1:3 / g:ml), so that it starts to precipitate, and 15g of sodium hydroxide solid is continuously added to adjust the pH value to 3-4, so that it completely precipitates, and then the precipitate is filtered to obtain filtrate and filter cake, the filtrate is retained, and the filter cake is washed with water five times, and after filtration, the obtained filter cake is placed in an oven at 110°C for 10-12 hours, and after complete drying, it is ground into powder, and the chemical composition is detected and analyzed, and the mass fraction of CaO and the mass fraction of Fe2O3 are enriched.

[0036] Example 3

[0037] A method for recovering calcium and iron by melting and wet separation of steel slag, comprising the following steps:

[0038] First, the steel slag is vibrated and broken to a particle size of less than 0.2 mm, ground into powder, and the ingredient content is detected to obtain the steel slag ingredient (see Table 1); the steel slag is mixed with a fluxing agent (fluxing agent 1: fluxing agent 2 = 2:1) at a mass ratio of 1:1, melted by a high-frequency sample melting machine, the tray rotation speed is 4 r / min, the temperature rising interval is (0-650, 650-1050) °C, and after cooling, a solid steel slag sample is formed, which is then crushed and ground into powder; the above powder-like steel slag sample is added with a 34% concentration hydrochloric acid solution at a solid-liquid ratio of 1:6.25 / g:ml, heated to 240°C and stirred until it is completely dissolved; 40% mass concentration hydrofluoric acid is added to the above mixed solution at a steel slag to hydrofluoric acid ratio of 1:2, and after constant temperature heating for 40 minutes, perchloric acid solution is added to the solution at a steel slag to perchloric acid solid-liquid ratio (1:0.8 / g:ml), and after constant temperature stirring for 15 minutes, the stirring is stopped and the temperature is lowered to room temperature; 200g / ml sodium hydroxide solution is added at a steel slag to sodium hydroxide solid-liquid ratio (1:2 / g:ml) to make it start to precipitate, while adjusting the solution pH value to be within 3-4, and 10g of sodium hydroxide solid is continuously added to make the precipitation complete; the above precipitation solution is filtered to obtain filtrate and filter cake, the filtrate is retained, and the obtained filter cake is washed with water for five times and then filtered again; the obtained filter cake is placed in an oven at 110°C for 10-12 hours, dried, then ground into powder, and the chemical composition is analyzed and detected (see Table 1). As shown in Table 1, the mass fraction of CaO is 61.312%, and the mass fraction of Fe2O3 is 35.792%

[0039] Example 4

[0040] A method for recovering calcium and iron by melting and wet separation of steel slag, comprising the following steps:

[0041] 4g of powdered steel slag is mixed with fluxing agent at a mass ratio of 1:1.5, and is melted by a high-frequency sample melting machine, with temperature control at (0-650, 650-1050) °C. After cooling, a solid solution is formed, which is then crushed and ground into powder. 34% concentrated hydrochloric acid is added to the powdered steel slag at a solid-liquid ratio of 1g:12ml, and is heated to 240°C and kept at this temperature. The mixture is stirred until it is completely dissolved. Then, 24.2ml of 40% hydrofluoric acid is added to the mixed solution, which is kept at 240°C for 40 minutes. Then, 9ml of perchloric acid solution is added, and the mixture is stirred for 15 minutes, and then the stirring is stopped and the temperature is lowered to room temperature. 20ml of NaOH (200g / ml) sodium hydroxide solution is added to the above solution, and the solution is adjusted to a pH of 3-4. Then, 13g of solid sodium hydroxide is added to the solution to completely precipitate the solution. The solution is filtered to obtain filtrate and filter cake. The filtrate is reserved, and the filter cake is washed with water five times and then filtered again. The filter cake is placed in an oven at 110°C for 10-12 hours, and then dried and ground into powder. The chemical composition of the powder is analyzed (see Table 1). As shown in Table 1, the mass fraction of CaO is 64.9%, and the mass fraction of Fe2O3 is 32.8%.

[0042] Example 5

[0043] A method for melting and wet separation and enrichment of calcium and iron from steel slag, comprising the following steps:

[0044] First, the steel slag is crushed by vibration to a particle size of less than 0.2mm, and is ground into powder. The composition of the steel slag is analyzed (see Table 1). The steel slag is mixed with fluxing agent (fluxing agent 1: fluxing agent 2 = 2:1) at a mass ratio of 1:1.5, and is melted by a high-frequency sample melting machine. The tray rotates at a speed of 4r / min, and the temperature is controlled at (0-650, 650-1050) °C. After cooling, a glassy phase steel slag sample is formed, which is then crushed and ground into powder. The powdered steel slag sample is added with 34% hydrochloric acid solution at a solid-liquid ratio of 1g:7.5ml, and is heated to 240°C and stirred until it is completely dissolved into a liquid. Then, 26ml of 40% hydrofluoric acid solution is added to the mixed solution, which is kept at a constant temperature for 40 minutes. Then, 10ml of perchloric acid solution is added to the solution, which is stirred at a constant temperature for 15 minutes, and then the stirring is stopped and the temperature is lowered to room temperature. 10ml of NaOH (400g / ml) sodium hydroxide solution is added to the above solution, and the pH of the solution is adjusted to 3-4. Then, 15g of solid sodium hydroxide is added to the solution to completely precipitate the solution. The precipitated solution is filtered to obtain filtrate and filter cake. The filtrate is reserved, and the filter cake is washed with water five times and then filtered again. The filter cake is placed in an oven at 110°C for 10-12 hours, and then dried and ground into powder. The chemical composition of the powder is analyzed (see Table 1). As shown in Table 1, the mass fraction of CaO is 59.6%, and the mass fraction of Fe2O3 is 38.5%.

[0045] Example 6

[0046] A method for recovering calcium and iron by melting-wet separation of steel slag, comprising the following steps:

[0047] The powdered steel slag (≤0.2mm) is mixed with fluxing agent (fluxing agent 1: fluxing agent 2 = 1:2) at a ratio of 1:15 (mass ratio), and is reacted (5-120min) at (800-1400℃) to completely melt it, and after cooling, a glassy phase steel slag sample is formed, which is then crushed and ground into powder (≤0.2mm), and concentrated hydrochloric acid is added to the steel slag at a solid-liquid ratio (1:15 / g:ml), and is fully stirred at 240℃ until it is completely dissolved, 20ml of 40% hydrofluoric acid is added to the mixed solution, and after 40min at 240℃, 10ml of perchloric acid is added, and after stirring for 15min, it is reduced to room temperature, then 30ml of NaOH (200g / ml) solution is added to make it start to precipitate, and 10g of solid sodium hydroxide is continuously added to adjust the pH value to 3-4 to make the precipitation complete, then the precipitate is filtered to obtain filtrate and filter cake, the filtrate is reserved, and after the filter cake is washed with water five times, it is filtered, and the obtained filter cake is placed in an oven at 110℃ for 10-12h, and after complete drying, it is ground into powder, and the chemical composition is detected and analyzed.

[0048] Table 1:

[0049]

[0050] Finally, it should be pointed out that the above only describes the preferred embodiments of the present application, and is not intended to limit the present application, and although the foregoing embodiments of the present application have been described in detail, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacements to some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for recovering calcium and iron by melting-wet separation and enrichment of steel slag, characterized by, The method comprises the following steps: (1) crushing the steel slag and detecting and controlling the ingredient content; (2) mixing the steel slag obtained in step (1) with a fluxing agent at a mass ratio of 1: (1-20) and then reacting at 800-1400 ℃ for 5-120 min to completely melt the mixture, and then cooling to form a glassy phase steel slag, and then crushing and grinding the glassy phase steel slag into a powder; (3) adding hydrochloric acid to the powder obtained in step (2) at a mass-volume ratio of 1 g: (3-20) ml, and stirring at a reaction temperature of 180-300 ℃ until a mixed solution is obtained; (4) adding hydrofluoric acid to the mixed solution obtained in step (3) at a mass-volume ratio of steel slag: hydrofluoric acid = 1 g: (1-5) ml, and then heating at 90-400 ℃ for 20-180 min, and then adding perchloric acid solution at a mass-volume ratio of steel slag: perchloric acid solution = 1 g: (0.5-2) ml, and then stirring at 90-400 ℃ for 20-180 min, and then stopping stirring and cooling to room temperature; (5) adding sodium hydroxide to the solution obtained in step (4) at a mass-volume ratio of steel slag: sodium hydroxide = 1 g: (0.5-3) ml, and then allowing the precipitate to completely precipitate; (6) filtering the precipitate solution obtained in step (5) to obtain a filtrate and a filter cake, and then repeatedly washing the filter cake with water, and then filtering the filter cake again; (7) placing the filter cake obtained in step (6) in an oven at 110 ℃ for 10-12 hours, and then drying the filter cake, and then grinding the dried filter cake into a powder, and then detecting and analyzing the powder.

2. The method according to claim 1, wherein the method is characterized by, The steel slag in step (1) is converter steel slag or electric furnace steel slag.

3. The method according to claim 1, wherein the method is characterized by, The ingredient content of the steel slag in step (1) is as follows: CaO: 20%-45%, Fe2O3: 10%-35%, SiO2: 10%-30%, Al2O3: 0.5%-9%, MgO: 2%-15%, V2O5: 0.2%-8%, TiO2: 0.2%-0.9%, SrO: 0.01%-0.08%, CuO: 0.01%-0.08%, and NbO: 0.02%-0.08%.

4. The method according to claim 1, wherein the method is characterized by, The fluxing agent in step (2) is one of sodium peroxide, lithium tetraborate, sodium carbonate, lithium metaborate, and boric acid, or a mixture of multiple thereof in any ratio.

5. The method according to claim 1, wherein the method is characterized by, The particle size of the powder in step (2) is ≤0.2 mm.

6. The method according to claim 1, wherein the method is characterized by, The mass concentration of the hydrochloric acid in step (3) is 30%-37%.

7. The method according to claim 1, wherein the method is characterized by, The stirring speed in step (4) is 30-180 r / min.

8. The method according to claim 1, wherein the method is characterized by, The mass concentration of the sodium hydroxide in step (5) is 200-400 g / L, and the solution PH is controlled to be 3-4.

9. The method according to claim 1, wherein the method is characterized by, The number of times of washing with water in step (6) is ≥5.

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