Method for efficiently recovering iron ore concentrate from iron-containing waste

Abstract

The invention belongs to the technical field of solid waste treatment and resource recovery, and particularly relates to a method for efficiently recovering iron ore concentrate from iron-containing waste. The method comprises the following treatment steps: (1) uniformly mixing the iron-containing waste with a concentrated alkali solution and an additive; (2) carrying out a hydrothermal reaction on the mixture, and after the hydrothermal reaction is finished, carrying out solid-liquid separation to obtain an iron-enriched phase and a concentrated alkali solution; and (3) washing the iron-enriched phase with hot water to obtain an iron-enriched phase and washing liquid, and carrying out magnetic separation on the iron-enriched phase to obtain iron ore concentrate and tailings. The method is short in technical process, iron resources can be efficiently recycled in the form of iron ore concentrate after one-step reaction, a high-temperature calcination environment of a pyrometallurgy means is not needed, the process energy consumption is low, the requirement for a device is low, and the treatment cost is low. The used concentrated alkali solution can be recycled, the washing liquid can also be returned to the concentrated alkali solution for repeated use, the consumption of chemical reagents is low, and wastewater and waste gas are nearly zero in emission.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste treatment and resource recovery, and particularly relates to a method for efficiently recovering iron concentrate from iron-containing waste. Background Art

[0002] With the continuous and rapid development of the steel and metallurgical industry, the total scale continues to expand. Steel production requires a large amount of iron ore as a production raw material. The supply of iron ore is difficult to meet the needs of economic growth, and there is an urgent need to develop new sources of iron ore.

[0003] The metallurgical industry, especially the nonferrous metallurgical industry, is accompanied by the emission of a large amount of iron-containing waste, such as red mud, ferrovanadium slag, ferrosulfide waste slag, etc. The emission volume is large, and most of them have not been effectively treated and utilized, but only stored through landfill and other methods, which has brought serious environmental risks and waste of resources.

[0004] A Chinese patent application document with publication number CN118639016A discloses a method for separating scandium and recovering iron and titanium from scandium-vanadium-titanium magnetite tailings. The method comprises drying and crushing the scandium-vanadium-titanium magnetite tailings, mixing them with titanium dioxide waste acid and coke to form pellets. The pellets are subjected to two-stage treatments of low-temperature sintering and high-temperature roasting, and then ball milled and subjected to multi-stage separation (weak magnetic separation, strong magnetic separation and gravity separation) to obtain iron concentrate, titanium concentrate, scandium concentrate and tailings. Finally, the scandium concentrate is added to titanium dioxide waste acid for leaching to obtain a scandium-containing leaching solution and leaching residue.

[0005] A Chinese patent document with the authorization number CN113528734B discloses a method for recovering iron concentrate by roasting and reducing iron-containing waste. A reducing atmosphere is introduced under air-tight conditions, and iron-containing waste residue or iron-containing sludge is mixed with an additive and then roasted and reduced to obtain a roasted material. The roasted material is magnetically separated and dried to obtain an iron concentrate.

[0006] The Chinese patent application document with publication number CN111940456A proposes a method for recovering iron concentrate by thermal decomposition-coupled reduction of iron-containing waste slag and organic solid waste. The method mixes iron-containing waste slag and organic solid waste, uses organic solid waste as a reduction source, conducts thermal decomposition-coupled reduction reaction, and magnetically separates the obtained reduced material to obtain iron concentrate.

[0007] The Chinese patent application document with publication number CN115094240A proposes a method for separating iron and lead and enriching iron in iron-containing waste slag, wherein the iron-containing waste slag is fully dispersed in a chloride solvent of a certain concentration at a certain solid-liquid ratio, placed in a hydrothermal kettle for hydrothermal reaction, and solid-liquid separation is performed after the reaction to obtain an iron-enriched precipitate and a lead-containing separation liquid.

[0008] In the above-mentioned prior art, there are still many shortcomings and deficiencies in recovering iron resources from iron-containing wastes, which are mainly reflected as follows:

[0009] (1) The use of pyrometallurgical methods (roasting, sintering and pyrolysis, etc.) to treat iron-containing waste still has the problems of high energy consumption, large amount of reducing gas / coke consumption, high production cost, and the emission of waste gas will cause secondary pollution;

[0010] (2) The use of hydrometallurgical methods requires the consumption of a large amount of chemical reagents such as acid or salt, and the iron resources obtained after treatment exist in the form of iron-enriched precipitates or iron element solutions containing a large amount of impurities such as salt, which is not conducive to efficient utilization;

[0011] (3) Some technical processes are lengthy and involve complicated steps. Summary of the invention

[0012] In view of the shortcomings and deficiencies of the above prior art, the object of the present invention is to provide a method for efficiently recovering iron concentrate from iron-containing waste. The method of the present invention can efficiently recover iron resources from iron-containing waste in the form of iron concentrate.

[0013] The purpose of the present invention is achieved through the following technical solutions:

[0014] A method for efficiently recovering iron concentrate from iron-containing waste comprises the following processing steps:

[0015] (1) uniformly mixing the iron-containing waste with the concentrated alkali solution and the additive;

[0016] (2) subjecting the mixture to a hydrothermal reaction, and after the hydrothermal reaction, solid-liquid separation is performed to obtain an iron-enriched phase and a concentrated alkaline solution;

[0017] (3) The iron-rich phase is washed with hot water to obtain an iron-rich phase and a washing liquid (a dilute alkaline solution), and the iron-rich phase is separated by magnetic separation to obtain iron concentrate and tailings.

[0018] Furthermore, in the step (1), the iron-containing waste is one or more of red mud, ferrovanadium slag, lead-zinc smelting slag, ferrosulfide waste slag and the like.

[0019] Furthermore, in the step (1), the particle size of the iron-containing waste is less than 0.25 mm, and the Fe content in the iron-containing waste is greater than 15 wt.%.

[0020] Furthermore, in step (1), the concentrated alkali solution is a sodium hydroxide solution or a potassium hydroxide solution having a concentration greater than 160 g / L; preferably a sodium hydroxide solution or a potassium hydroxide solution having a concentration of 160 to 300 g / L.

[0021] Furthermore, in the step (1), the volume mass ratio of the concentrated alkaline solution to the iron-containing waste is 3 to 20 mL / g.

[0022] Furthermore, in the step (1), the additive is a reducing organic substance containing an amine group or an alcohol group; preferably, the additive is one or more of ethylenediamine, propylene glycol, triethanolamine, and ethylene glycol.

[0023] Furthermore, in the step (1), the amount of the additive is 0.5% to 20% of the mass of the iron-containing waste.

[0024] Furthermore, in the step (2), the temperature of the hydrothermal reaction is 200 to 350° C., preferably 230 to 290° C.; and the time of the hydrothermal reaction is 30 to 210 min.

[0025] Furthermore, in the step (2), the concentrated alkaline solution after the hydrothermal reaction is returned to the hydrothermal reaction for repeated use.

[0026] Furthermore, in step (3), the temperature of the hot water washing is 45 to 90° C., the amount of water used for the hot water washing is 1 to 6 times the mass of the iron-enriched phase, and the number of hot water washings is 1 to 3 times.

[0027] Furthermore, in the step (3), the washing liquid (dilute alkali solution) is concentrated by evaporation to recover alkali for preparing a concentrated alkali solution.

[0028] Furthermore, in the step (3), the magnetic separation is preferably wet magnetic separation, the magnetic field strength is 100 to 800 mT, and the magnetic separation time is 3 to 15 min.

[0029] Furthermore, in the step (3), the Fe content of the iron ore concentrate is greater than 50 wt.%.

[0030] The principle of the present invention is that in a concentrated alkaline hydrothermal environment, most impurities in the iron-containing waste are dissolved and separated from the iron phase, and at the same time, the added additives are catalytically dissociated into reducing groups in the concentrated alkaline hydrothermal environment, so that the iron phase in the iron-containing waste is directionally reduced to Fe3O4 (magnetite), so that the solid phase after the reaction can be separated and enriched through a magnetic separation process to obtain iron concentrate.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The method for efficiently recovering iron concentrate from iron-containing wastes of the present invention has a short technical process, and the iron concentrate can be sorted out after a one-step reaction.

[0033] (2) The method of the present invention does not require a high-temperature calcination environment of pyrometallurgical methods, has low process energy consumption, low requirements for equipment, and low processing costs.

[0034] (3) The concentrated alkali solution used in the method of the present invention can be recycled, and the washing liquid can also be returned to the concentrated alkali solution for repeated use, the consumption of chemical reagents is low, and the discharge of waste water and waste gas is close to zero. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 A schematic flow chart of a method for efficiently recovering iron concentrate from iron-containing waste in an embodiment of the present invention;

[0036] Figure 2 The scanning electron microscope images of the red mud (a) before the reaction and the iron concentrate (b) finally obtained in Example 1 of the present invention are shown;

[0037] Figure 3 The scanning electron microscope images of the lead-zinc smelting slag (a) before the reaction and the iron concentrate (b) finally obtained in Example 2 of the present invention;

[0038] Figure 4 The scanning electron microscope images of the ferrosulphide waste slag (a) before the reaction and the final iron concentrate (b) obtained in Example 3 of the present invention;

[0039] Figure 5 The scanning electron microscope images are of the red mud (a) before the reaction and the iron concentrate (b) finally obtained in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0040] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0041] Example 1

[0042] A method for efficiently recovering iron concentrate from iron-containing waste, the processing flow diagram of which is shown in FIG. Figure 1 As shown, the specific processing steps include the following:

[0043] (1) Prepare 290 g / L sodium hydroxide solution, add 10 g red mud (Fe 28.22%) and 2.0 g triethanolamine into 85 mL of 290 g / L sodium hydroxide solution and mix well.

[0044] (2) The mixed material of step (1) is placed in a reactor for hydrothermal reaction at a reaction temperature of 290° C. and a reaction time of 200 min. After the reaction is completed, solid-liquid separation is performed to obtain an iron-enriched phase and a concentrated alkaline solution, and the concentrated alkaline solution can be further used for the reaction with the iron-containing waste.

[0045] (3) The iron-enriched phase obtained in step (2) is washed with hot water at 80° C., the amount of water used for washing is twice the mass of the iron-enriched phase, and the number of washing times is 3 times. The iron-rich solid phase obtained after washing enters a wet magnetic separator and is subjected to magnetic separation for 4 minutes under the condition of a magnetic field strength of 300 mT to obtain an iron concentrate. The washing liquid (dilute alkaline solution) after washing is evaporated and concentrated to recover the alkali for preparing a concentrated alkaline solution.

[0046] The Fe content and iron recovery of the red mud before treatment and the final iron concentrate measured by ICP-OES are listed in Table 1.

[0047] Table 1 Fe content and iron recovery rate of red mud and final iron concentrate

[0048] sample Fe content / % Iron recovery rate / % Red Mud 28.22 / Iron Concentrate 62.93 76.52

[0049] The scanning electron microscope images of the red mud before the reaction and the final iron concentrate obtained in this example are shown in the attached figure. Figure 2 As shown, it can be seen that octahedral Fe3O4 (magnetite) is obtained after hydrothermal reaction and magnetic separation of irregularly shaped red mud particles.

[0050] Example 2

[0051] A method for efficiently recovering iron concentrate from iron-containing waste, the processing flow diagram of which is shown in FIG. Figure 1 As shown, the specific processing steps include the following:

[0052] (1) Prepare 170 g / L sodium hydroxide solution, add 10 g of lead-zinc smelting slag (Fe 19.53%) and 2.0 g of glycerol into 40 mL of 170 g / L sodium hydroxide solution and mix well.

[0053] (2) The mixed material of step (1) is placed in a reactor for hydrothermal reaction at a reaction temperature of 255° C. and a reaction time of 45 min. After the reaction is completed, solid-liquid separation is performed to obtain an iron-enriched phase and a concentrated alkaline solution, and the concentrated alkaline solution can be further used for the reaction with the iron-containing waste.

[0054] (3) The iron-enriched phase obtained in step (2) is washed with hot water at 80° C., the amount of water used for washing is 3 times the mass of the iron-enriched phase, and the number of washing times is 1. The iron-rich solid phase obtained after washing enters a magnetic separator and is subjected to magnetic separation for 12 minutes under a magnetic field strength of 700 mT to obtain an iron concentrate. The washing liquid (dilute alkaline solution) after washing is evaporated and concentrated to recover the alkali for preparing a concentrated alkaline solution.

[0055] The Fe content and iron recovery rate of the lead-zinc smelting slag before treatment and the final iron concentrate measured by ICP-OES are listed in Table 2.

[0056] Table 2 Fe content and iron recovery rate of lead-zinc smelting slag and final iron concentrate

[0057]

[0058]

[0059] The scanning electron microscope images of the lead-zinc smelting slag before the reaction and the final iron concentrate obtained in this embodiment are shown in the attached figure. Figure 3 As shown, it can be seen that regular angular blocks of Fe3O4 (magnetite) are obtained after hydrothermal reaction and magnetic separation of flaky and flocculent particles of lead-zinc smelting slag.

[0060] Example 3

[0061] A method for efficiently recovering iron concentrate from iron-containing waste, the processing flow diagram of which is shown in FIG. Figure 1 As shown, the specific processing steps include the following:

[0062] (1) Prepare 230 g / L potassium hydroxide solution, add 10 g of ferrosulphide waste slag (Fe 30.02%), 0.4 g of ethylenediamine and 0.5 g of ethylene glycol into 55 mL of 230 g / L potassium hydroxide solution and mix well.

[0063] (2) The mixed material of step (1) is placed in a reactor for hydrothermal reaction at a reaction temperature of 265° C. for a reaction time of 100 min. After the reaction is completed, solid-liquid separation is performed to obtain an iron-enriched phase and a concentrated alkaline solution, and the concentrated alkaline solution can be further used for the reaction with the iron-containing waste.

[0064] (3) The iron-enriched phase obtained in step (2) is washed with hot water at 80° C., the amount of water used for washing is 1 times the mass of the iron-enriched phase, and the number of washing times is 3 times. The iron-rich solid phase obtained after washing enters a magnetic separator and is subjected to magnetic separation for 7 minutes under a magnetic field strength of 500 mT to obtain an iron concentrate. The washing liquid (dilute alkaline solution) after washing is evaporated and concentrated to recover the alkali for preparing a concentrated alkaline solution.

[0065] The Fe contents and iron recovery rates of the pyrite slag and iron concentrate before treatment measured by ICP-OES are listed in Table 3.

[0066] Table 3 Fe content and iron recovery rate of ferrosulphide waste slag and final iron concentrate

[0067] Fe content / % Iron recovery rate / % Sulfur iron waste 30.02 / Iron Concentrate 57.69 82.31

[0068] The scanning electron microscope images of the ferrosulphide waste slag before the reaction and the final iron concentrate obtained in this embodiment are shown in the attached figure. Figure 4 As shown, it can be seen that regular octahedral Fe3O4 (magnetite) is obtained after hydrothermal reaction and magnetic separation of prismatic and strip-shaped ferrosulphide waste slag.

[0069] Comparative Example 1

[0070] A method for efficiently recovering iron concentrate from iron-containing wastes. Compared with Example 1, the additive triethanolamine is not added, and the rest is the same.

[0071] The Fe content and iron recovery rate of the red mud before treatment and the final iron concentrate obtained in this comparative example are listed in Table 4.

[0072] Table 4 Fe content and iron recovery rate of red mud and final iron concentrate

[0073] sample Fe content / % Iron recovery rate / % Red Mud 28.22 / Iron Concentrate 31.76 16.22

[0074] The scanning electron microscope images of the red mud before the reaction and the final iron concentrate obtained in this comparative example are shown in the attached figure. Figure 5 As shown, due to the lack of additives, the irregular and fine red mud particles are not converted into magnetite after the reaction, but remain in the form of spherical Fe2O3 (hematite) and a small amount of angular blocky γ-Fe2O3 (magnetic hematite), resulting in poor effect of magnetic separation enrichment and recovery of iron, and unable to achieve the purpose of efficient recovery of iron resources.

[0075] Comparative Example 2

[0076] A method for efficiently recovering iron concentrate from iron-containing wastes. Compared with Example 1, a room temperature alkaline leaching reaction is used instead of a 290° C. hydrothermal reaction, and the rest is the same.

[0077] The Fe content and iron recovery rate of the red mud before treatment and the final iron concentrate obtained in this comparative example are listed in Table 5.

[0078] Table 5 Fe content and iron recovery rate of red mud and final iron concentrate

[0079] sample Fe content / % Iron recovery rate / % Red Mud 28.22 / Iron Concentrate 41.76 0.27

[0080] Since iron-containing components and additives are difficult to react with alkaline solutions at room temperature, the state of red mud basically does not change before and after the reaction, so it is impossible to recover iron resources from red mud through magnetic separation.

[0081] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for efficiently recovering iron concentrate from iron-containing waste, characterized in that: The processing steps include: (1) uniformly mixing the iron-containing waste with the concentrated alkali solution and the additive; (2) subjecting the mixture to a hydrothermal reaction, and after the hydrothermal reaction, solid-liquid separation is performed to obtain an iron-enriched phase and a concentrated alkaline solution; (3) The iron-rich phase is washed with hot water to obtain an iron-rich phase and a washing liquid, and the iron-rich phase is separated by magnetic separation to obtain iron concentrate and tailings.

2. A method for efficiently recovering iron concentrate from iron-containing waste according to claim 1, characterized in that: In the step (1), the iron-containing waste is one or more of red mud, ferrovanadium slag, lead-zinc smelting slag, and ferrosulfide waste slag.

3. A method for efficiently recovering iron concentrate from iron-containing waste according to claim 2, characterized in that: In the step (1), the particle size of the iron-containing waste is less than 0.25 mm, and the Fe content in the iron-containing waste is greater than 15 wt.%.

4. A method for efficiently recovering iron concentrate from iron-containing waste according to claim 1, characterized in that: In the step (1), the concentrated alkali solution is a sodium hydroxide solution or a potassium hydroxide solution with a concentration greater than 160 g / L; the volume mass ratio of the concentrated alkali solution to the iron-containing waste is 3 to 20 mL / g.

5. The method for efficiently recovering iron concentrate from iron-containing waste according to claim 1, characterized in that: In the step (1), the additive is a reducing organic matter containing an amine group or an alcohol group; the amount of the additive used is 0.5% to 20% of the mass of the iron-containing waste.

6. A method for efficiently recovering iron concentrate from iron-containing waste according to claim 5, characterized in that: The additive is one or more of ethylenediamine, propylene glycol, triethanolamine and ethylene glycol.

7. A method for efficiently recovering iron concentrate from iron-containing waste according to claim 1, characterized in that: In the step (2), the temperature of the hydrothermal reaction is 200-350° C., and the time of the hydrothermal reaction is 30-210 min; the concentrated alkaline solution after the hydrothermal reaction is returned to the hydrothermal reaction for repeated use.

8. The method for efficiently recovering iron concentrate from iron-containing waste according to claim 1, characterized in that: In the step (3), the temperature of the hot water washing is 45-90° C., the amount of water used for the hot water washing is 1-6 times the mass of the iron-enriched phase, and the number of hot water washings is 1-3 times; the washing liquid is concentrated by evaporation to recover alkali for preparing a concentrated alkali solution.

9. The method for efficiently recovering iron concentrate from iron-containing waste according to claim 1, characterized in that: In the step (3), the magnetic separation is wet magnetic separation, the magnetic field strength is 100 to 800 mT, and the magnetic separation time is 3 to 15 minutes.

10. The method for efficiently recovering iron concentrate from iron-containing waste according to claim 1, characterized in that: In the step (3), the Fe content of the iron ore concentrate is greater than 50 wt.%.

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