Method for preparing fine iron powder by removing impurities from hydrometallurgy hematite slag

Abstract

A method for preparing a fine iron powder by removing impurities from hydrometallurgy hematite slag, belonging to the technical field of chemical metallurgy. The present method comprises: subjecting hematite slag produced during a hydrometallurgy process to acid dissolution for impurity removal, washing and filtering same, then mixing the hematite slag with a carbonaceous reducing agent, heating the mixed product to 800-1350°C by means of gas combustion, maintaining the temperature to perform a reaction for 1-4 h, and after the reaction is finished, subjecting same to rapid cooling, fine grinding and magnetic separation, so as to obtain a fine iron powder containing more than or equal to 70% of iron, less than or equal to 0.5% of zinc, less than or equal to 3.0% of sulfur, less than or equal to 0.1% of copper, less than or equal to 0.1% of lead, less than or equal to 0.1% of arsenic, less than or equal to 0.05% of phosphorus, and less than or equal to 1.5% of SiO2. The present method can achieve the deep removal of residual impurities in hematite slag and obtain a high-quality fine iron powder, and has the advantages of a high resource utilization rate of hematite slag, a good impurity removal efficiency, fine iron powder being of good quality, etc.

Description

A method for preparing iron concentrate from hematite slag in hydrometallurgical process Technical Field

[0001] This invention relates to a method for preparing iron concentrate from hematite slag using hydrometallurgical processes, belonging to the field of chemical metallurgical technology. Background Technology

[0002] Separating precipitated iron ions from hydrometallurgical solutions is an indispensable process in the hydrometallurgical processes of non-ferrous metals such as zinc, nickel, copper, and cobalt, and it is also one of the technical challenges of hydrometallurgical processes.

[0003] To address the challenges of separating and precipitating iron from iron-containing solutions in hydrometallurgical processes, domestic and international scientists have conducted extensive research, developing various iron removal methods, including hydrolysis, jaundice ferrous sulfate removal, goethite removal, and hematite removal. These methods have effectively separated iron from non-ferrous metals such as zinc, nickel, copper, cobalt, cadmium, indium, and germanium in the leachate, reducing iron slag production and minimizing the loss of valuable metals like zinc, nickel, cobalt, copper, lead, cadmium, indium, and germanium in iron-containing waste slag. This has increased the recovery rate of valuable metals and promoted the advancement and development of hydrometallurgical technology. Among these methods, the hematite removal process precipitates ferrous sulfate in solutions containing sulfates such as zinc sulfate and nickel sulfate as hematite. Compared to other methods, the hematite removal process offers advantages such as high iron content in the precipitated product, high precipitation efficiency, and good crystallization and filtration properties of the precipitate, making it one of the main technologies for iron removal in hydrometallurgy. However, in actual production, the hematite slag produced by the hydrometallurgical solution hematite removal method still contains high levels of heavy metal ions and impurities such as zinc, copper, cadmium, lead, arsenic, and sulfur, making it difficult to directly utilize the hematite slag for high-value resource utilization, and posing an environmental pollution risk during the stockpiling process. Technical issues

[0004] Therefore, how to deeply remove heavy metal ions and impurity elements from the hematite slag produced in the hematite removal process of hydrometallurgical iron removal, reduce the heavy metal content, improve the quality of iron-containing products, and expand the application fields are technical problems that need to be studied and solved. Technical solutions

[0005] To address the shortcomings of high heavy metal impurity content in hydrometallurgical hematite slag, which hinders resource utilization, this invention provides a method for preparing iron concentrate from hydrometallurgical hematite slag. The method involves stepwise and deep removal of impurities such as zinc sulfate, copper sulfate, lead sulfate, arsenates, basic ferric sulfate, and cadmium-containing sulfates from the hematite slag through acid dissolution pre-removal, high-temperature reduction deep removal, removal of bound oxygen, and magnetic separation. Simultaneously, under high-temperature reduction conditions, the bound oxygen of volatile impurities is partially removed, crystal water is removed, the heavy metal content in the hematite slag is reduced, and the purity of iron compounds is improved. The reaction products are then cooled, finely ground, and magnetically separated to produce high-quality iron concentrate, thus expanding the resource utilization pathways of hematite slag.

[0006] This invention discloses a method for preparing iron concentrate from hematite slag produced by hydrometallurgical processes. The specific operation includes: removing impurities from hematite slag produced by hydrometallurgical processes using dilute sulfuric acid solution, washing and filtering, mixing with a carbonaceous reducing agent, introducing gas into the mixture for combustion while ensuring the reaction temperature is greater than or equal to 800°C, reacting for at least 1 hour, rapidly cooling after the reaction, fine grinding and magnetic separation to obtain iron concentrate. The concentration of the dilute acid is 10 g / L to 50 g / L, and the liquid-to-solid ratio of the dilute sulfuric acid solution to the hematite slag, expressed as mL:g, is 2 to 5:1, preferably 3 to 5:1.

[0007] As a preferred embodiment, the present invention provides a method for preparing iron concentrate from hydrometallurgical hematite slag after impurity removal, comprising the following steps:

[0008] (1) Acid dissolution and impurity removal of hematite slag: The hematite slag from hydrometallurgical process is reacted with a sulfuric acid solution with a concentration of 10 g / L to 50 g / L, preferably 10 to 20 g / L, to remove impurities. After the reaction is completed, the liquid and solid are separated to obtain filter residue with a water content of 8 wt% to 15 wt%.

[0009] (2) Mixing: The filter residue produced in step (1) is mixed with carbonaceous reducing agent. The proportion of carbonaceous reducing agent is 0-25% of the weight of filter residue, preferably 5%-21%, and more preferably 10-21%.

[0010] (3) Reduction and purification: Gas is introduced into the mixture produced in step (2) and combustion is carried out, and the reaction temperature is ensured to be 800~1350℃, preferably 800~1200℃. The reaction is carried out for 1h~4h to reduce and remove impurities. After the reaction is completed, the mixture is cooled down.

[0011] (4) Fine grinding and magnetic separation: The product of step (3) is finely ground and magnetically separated to obtain high-quality iron concentrate.

[0012] In this invention, a concentration of 10 g / L to 50 g / L is selected, and the liquid-to-solid ratio of the dilute sulfuric acid solution to the hematite slag is controlled at 2 to 5:1 (mL:g). This is because, under these conditions, the reaction between the dilute acid (including dilute sulfuric acid) and iron oxides is weak, resulting in a low dissolution rate of iron oxides. However, the dilute acid possesses strong impurity removal capabilities, dissolving zinc sulfate, basic sulfates, hydroxides, etc., in the hematite. This ensures, to a certain extent, the depth of impurity removal and the effective recovery rate of iron resources. Further optimization is then performed, and with the coordination of various parameters, the iron recovery rate and the iron content in the resulting product can be improved (e.g., through two magnetic separations, an iron content greater than 85% and an iron recovery rate greater than 94% can be obtained). Furthermore, by adjusting the particle size parameters of the hematite slag, impurities can be further removed. Therefore:

[0013] In step (1), the particle size of the hematite slag is controlled to be ≤74 micrometers.

[0014] The hydrometallurgical hematite slag of this invention comprises: hematite slag produced from iron-containing solutions in hydrometallurgical processes of zinc, nickel, cobalt, copper, etc., through iron ore precipitation. By mass percentage, it contains: Fe 45%~65%, Zn 1%~5%, S 2%~10%. As a further preferred embodiment, its main chemical composition (wt%) is: Fe 45%~65%, Zn 1%~5%, S 2%~10%, Cu ≤1%, Ni content ≤1.0%, and Co content ≤1.0%.

[0015] In step (1) of this invention, the hydrometallurgical hematite slag is placed in a sulfuric acid solution with a sulfuric acid concentration of 10 g / L to 50 g / L, preferably 10 to 20 g / L, and reacted at 40 to 80°C for 20 to 60 minutes to complete the initial impurity removal.

[0016] In this invention, in step (1), controlling the water content of the filter residue to 10wt%~20wt% allows for thorough and uniform mixing of the hematite slag and carbonaceous reducing agent, improving the reduction effect while preventing dust from flying and improving the environment. Combined with the subsequently introduced coal gas, it can reduce the iron oxide in the hematite slag to ferric oxide.

[0017] In step (1) of this invention, the carbonaceous reducing agent is selected from one or more of coke powder, anthracite, coking coal, and reducing coal.

[0018] In this invention, the reduction temperature in step (3) is further preferably 900℃~1200℃, even more preferably 1000℃~1200℃, and even more preferably 1000℃~1080℃ because: if the temperature is too low, the removal efficiency of impurities such as zinc and sulfur will be low, and the quality of iron concentrate will be poor; if the temperature is too high, the energy consumption will be too high and the reaction products will agglomerate. The reaction time is controlled to be 1h~4h because: if the reaction time is too short, the reaction will be insufficient, and the removal efficiency of impurities such as zinc and sulfur will be poor; if the reaction time is too long, the production efficiency will be low and the energy consumption will be high.

[0019] In industrial applications, it is also necessary to control the oxygen concentration in the flue gas at the reaction endpoint to be below 10%.

[0020] In the optimized step (4), the particle size of the material is controlled to be ≤74μm during fine grinding and the magnetic field strength of the magnetic separation process is 800~2000 Oe.

[0021] As one of the optimal methods, the hematite slag from hydrometallurgical processes is reacted with a sulfuric acid solution of 10 g / L to 12 g / L at a liquid-to-solid ratio (mL / g) of 3.9 to 4.1:1 for acid dissolution and impurity removal. After the reaction, the liquid and solid are separated to obtain a filter residue with a water content of 12 wt% to 13 wt%. The filter residue is then uniformly mixed with anthracite, with the amount of anthracite added being 18 to 21% of the weight of the hematite slag. The mixed product is heated to 1040℃ to 1060℃ in a tubular furnace using gas combustion for a reaction time of 170 to 190 min, with the oxygen concentration in the flue gas controlled to be less than 6.0% at the end of the reaction. The reaction product is then rapidly cooled with nitrogen blast and finely ground to a particle size of ≤74 μm. It is then magnetically separated twice under a magnetic field strength of 1800 Oe. The iron concentrate obtained from the two magnetic separations has an iron content greater than 87 wt% and an iron recovery rate greater than 97%. Beneficial effects

[0022] (1) This invention can efficiently remove various heavy metals such as zinc, copper, nickel, cobalt, lead, arsenic, and cadmium, as well as impurities such as sulfur and phosphorus, from hydrometallurgical hematite slag, while reducing the bound oxygen in the hematite slag, increasing the iron content, producing high-quality iron concentrate, and realizing the resource utilization of hematite slag.

[0023] (2) The present invention employs a combination of multiple technical means such as acid dissolution for impurity removal, high-temperature reduction for impurity removal, and magnetic separation to achieve stepwise removal of heavy metals and impurity elements in different phases such as zinc, copper, nickel, cobalt, cadmium sulfate, basic ferric sulfate, arsenate, adsorbed sulfate, and lead sulfate in hydrometallurgical hematite slag. It has the advantage of being able to remove a variety of impurity elements that are difficult to dissolve and difficult to volatilize from hematite slag, and the synergistic removal efficiency of heavy metals and impurity elements such as phosphorus and sulfur is high.

[0024] (3) The present invention has a good effect on removing impurity components, low iron loss rate, high iron recovery rate and high iron resource utilization rate.

[0025] (4) The iron concentrate produced by the present invention is of high quality, exceeding the relevant industry standard requirements for iron concentrate by-products of non-ferrous metal smelting. After optimization, the iron concentrate produced has the following contents: iron content ≥85%, zinc content ≤0.5%, copper content ≤0.1%, nickel content ≤0.1%, cobalt content ≤0.1%, cadmium content ≤0.1%, lead content ≤0.1%, arsenic ≤0.1%, sulfur content ≤1.5%, and phosphorus content ≤0.05%. Attached Figure Description

[0026] Figure 1 is a SEM image of the iron concentrate prepared in Example 1;

[0027] As can be seen from Figure 1, the iron powder prepared by this invention has a relatively uniform particle size distribution and a large specific surface area, and the resulting particles exhibit a distinct secondary particle state. Embodiments of the present invention

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] Example 1-1

[0030] A method for preparing iron concentrate from hematite slag produced by hydrometallurgical processes is as follows: 1000g of hematite slag produced by hydrometallurgical zinc smelting is taken. Its chemical composition (wt%) is: iron 57.0%, zinc 1.5%, copper 0.15%, nickel 0.11%, cobalt 0.02%, cadmium 0.15%, lead 0.20%, arsenic 0.18%, sulfur 4.5%, phosphorus 0.10%, with the remainder being oxygen. 3000mL of sulfuric acid solution with a concentration of 20g / L is added (liquid-to-solid ratio (mL / g) is 3:1), and the mixture is stirred at 60℃ for 30min. After the reaction, the solid and liquid components are separated using a centrifuge to obtain filter residue containing 12wt% water. The filter residue is then mixed evenly with 100g of coke powder, the amount of coke powder being 10% of the weight of the hematite slag. The mixed products were heated to 1000℃ by direct combustion of coal gas in a tubular furnace (with the coal gas in direct contact with the mixed products) for 2 hours, and the oxygen concentration in the flue gas was controlled to be 5% at the end of the reaction. The reaction products were rapidly cooled and then finely ground to a particle size of ≤74μm. The products were then magnetically separated twice under a magnetic field strength of 800 Oe. The product obtained from the first magnetic separation, by mass percentage, contained 76.0% iron, 0.30% zinc, 0.05% copper, 0.02% nickel, 0.01% cobalt, 0.05% cadmium, 0.03% lead, 0.05% arsenic, 1.25% sulfur, and 0.01% phosphorus. The iron concentrate obtained from the two magnetic separation processes contains, by mass percentage, 82.5% iron, 0.20% zinc, 0.01% copper, 0.01% nickel, 0.01% cobalt, 0.02% cadmium, 0.01% lead, 0.01% arsenic, 0.82% sulfur, and 0.01% phosphorus, with the remainder being oxygen and trace amounts of carbon.

[0031] The iron recovery rate was 95.6%.

[0032] Examples 1-2

[0033] The raw materials used are the same as in Examples 1-1, except that the amount of coke powder added is 15% of the weight of hematite slag; the iron concentrate obtained from the two magnetic separations contains, by mass percentage, 85.8% iron, 0.18% zinc, 0.01% copper, 0.01% nickel, 0.01% cobalt, 0.01% cadmium, 0.01% lead, 0.01% arsenic, 1.23% sulfur, and 0.01% phosphorus, with the remainder being oxygen and trace amounts of carbon.

[0034] The iron recovery rate was 94.3%.

[0035] Examples 1-3

[0036] The raw materials used are the same as in Examples 1-1, except that the mixed product is heated to 1350°C by gas combustion in a tube furnace; the iron concentrate obtained by two magnetic separations contains, by mass percentage, 94.5% iron, 0.11% zinc, 0.01% copper, 0.01% nickel, 0.01% cobalt, 0.01% cadmium, 0.01% lead, 0.01% arsenic, 0.85% sulfur, and 0.01% phosphorus, with the remainder being oxygen and trace amounts of carbon.

[0037] The iron recovery rate was 95.0%.

[0038] Examples 1-4

[0039] The raw materials used are the same as in Examples 1-1, except that the mixed product is heated to 800°C by gas combustion in a tube furnace; the iron concentrate obtained by two magnetic separations contains, by mass percentage, 75.2% iron, 0.50% zinc, 0.08% copper, 0.07% nickel, 0.06% cobalt, 0.1% cadmium, 0.1% lead, 0.08% arsenic, 2.85% sulfur, and 0.06% phosphorus, with the remainder being oxygen and carbon.

[0040] The iron recovery rate was 94.2%.

[0041] Examples 1-5

[0042] The raw materials used are the same as in Examples 1-1, except that: the mixed product is heated to 1000°C by gas combustion in a tube furnace and held for 3 hours; the iron concentrate obtained by two magnetic separations contains, by mass percentage, 91.7% iron, 0.15% zinc, 0.01% copper, 0.01% nickel, 0.01% cobalt, 0.01% cadmium, 0.01% lead, 0.01% arsenic, 0.50% sulfur, and 0.01% phosphorus, with the remainder being oxygen and trace amounts of carbon.

[0043] The iron recovery rate was 94.2%.

[0044] Examples 1-6

[0045] The raw materials used are the same as those in Example 1-1, except that 4000 mL of sulfuric acid solution with a concentration of 50 g / L is added (liquid-to-solid ratio (mL / g) is 4:1).

[0046] The iron concentrate obtained from the two magnetic separation processes contains, by mass percentage, 85.6% iron, 0.15% zinc, 0.01% copper, 0.01% nickel, 0.01% cobalt, 0.02% cadmium, 0.01% lead, 0.01% arsenic, 0.82% sulfur, and 0.01% phosphorus, with the remainder being oxygen and carbon.

[0047] The iron recovery rate was 91.0%.

[0048] Example 2

[0049] A method for preparing iron concentrate from hematite slag produced by hydrometallurgical processes is as follows: 1000g of hematite slag produced by hydrometallurgical zinc smelting is taken. Its chemical composition is as follows: hematite slag contains 55.0% iron, 1.5% zinc, 0.12% copper, 0.10% nickel, 0.03% cobalt, 0.11% cadmium, 0.21% lead, 0.10% arsenic, 3.2% sulfur, and 0.10% phosphorus. 4000mL of sulfuric acid solution with a concentration of 30g / L is added (liquid-to-solid ratio (mL / g) is 4:1), and the mixture is stirred and reacted at 40℃ for 30min. After the reaction, the solid and liquid components are separated using a centrifuge to obtain filter residue containing 10wt% water. Without adding coke powder, anthracite, or high-quality coal as reducing agents, the mixed product is heated to 1200℃ in a tubular furnace using coal gas combustion for 1h, controlling the oxygen concentration in the flue gas at the reaction endpoint to be less than 5.0%. The reaction product was rapidly cooled by nitrogen blasting and then finely ground to a particle size of ≤74μm. It was then magnetically separated twice under a magnetic field strength of 1200 Oe. The iron concentrate obtained from the two magnetic separations contained, by mass percentage, 92.3% iron, 0.21% zinc, 0.03% copper, 0.02% nickel, 0.002% cobalt, 0.02% cadmium, 0.01% lead, 0.02% arsenic, 0.95% sulfur, and 0.02% phosphorus, with the remainder being oxygen and trace amounts of carbon.

[0050] The iron recovery rate was 96.5%.

[0051] Example 3

[0052] A method for preparing iron concentrate from hematite slag produced by hydrometallurgical processes is as follows: 1000g of hematite slag produced by nickel hydrometallurgy is taken, with the following chemical composition (wt%): iron 62.5%, zinc 0.01%, copper 0.02%, nickel 0.5%, cobalt 0.04%, cadmium 0.01%, lead 0.01%, arsenic 0.08%, sulfur 3.0%, and phosphorus 0.10%. 4000mL of sulfuric acid solution with a concentration of 40g / L is added (liquid-to-solid ratio (mL / g) is 4:1), and the mixture is stirred and reacted at 40℃ for 50min. After the reaction, the solid and liquid components are separated using a centrifuge to obtain filter residue containing 8wt% water. The filter residue is then mixed evenly with 150g of coke powder, the amount of coke powder being 15% of the weight of the hematite slag. The mixed products were heated to 900℃ in a tubular furnace using coal gas combustion for 3 hours, with the oxygen concentration in the flue gas controlled to be less than 5.0% at the end of the reaction. The reaction products were then rapidly cooled using nitrogen blast and finely ground to a particle size of ≤74μm. They were then magnetically separated twice under a magnetic field strength of 1000 Oe. The resulting iron concentrate, obtained from the two magnetic separations, contained, by mass percentage, 78.6% iron, 0.005% zinc, 0.01% copper, 0.10% nickel, 0.02% cobalt, 0.01% cadmium, 0.01% lead, 0.03% arsenic, 0.85% sulfur, and 0.01% phosphorus, with the remainder being oxygen and trace amounts of carbon.

[0053] The iron recovery rate was 96.5%.

[0054] Example 4

[0055] A method for preparing iron concentrate from hematite slag produced by hydrometallurgical processes is as follows: 1000g of hematite slag produced by cobalt hydrometallurgy is taken. Its chemical composition is as follows: 58.0% iron, 0.01% zinc, 0.03% copper, 0.35% nickel, 0.75% cobalt, 0.15% cadmium, 0.12% lead, 0.01% arsenic, 3.5% sulfur, and 0.18% phosphorus. 3000mL of a 50g / L sulfuric acid solution is added (liquid-to-solid ratio (mL / g) is 3:1), and the mixture is stirred at 80℃ for 60min. After the reaction, the solid and liquid components are separated using a centrifuge to obtain filter residue containing 15wt% water. The filter residue is then mixed evenly with 150g of high-quality coal, the amount added being 15% of the weight of the hematite slag. The mixed products were heated to 900℃ in a tubular furnace using coal gas combustion for 1.5 hours, with the oxygen concentration in the flue gas controlled to be less than 3.5% at the end of the reaction. The reaction products were then rapidly cooled using nitrogen blast and finely ground to a particle size of ≤74μm. They were then magnetically separated twice under a magnetic field strength of 1500 Oe. The resulting iron concentrate, obtained from the two magnetic separations, contained, by mass percentage, 78.1% iron, 0.003% zinc, 0.05% copper, 0.1% nickel, 0.20% cobalt, 0.01% cadmium, 0.01% lead, 0.005% arsenic, 1.35% sulfur, and 0.01% phosphorus, with the remainder being oxygen and trace amounts of carbon.

[0056] The iron recovery rate was 96.2%.

[0057] Example 5

[0058] A method for preparing iron concentrate from hematite slag produced by hydrometallurgical processes is disclosed, the specific operation of which is as follows: 1000g of hematite slag produced by copper hydrometallurgy is taken, the chemical composition of which is: iron content 58.6%, zinc content 0.01%, copper content 1.52%, nickel content 0.12%, cobalt content 0.10%, cadmium content 0.12%, lead content 0.10%, arsenic content 0.15%, sulfur content 3.8%, and phosphorus content 0.11%. 4000mL of sulfuric acid solution with a concentration of 10g / L is added (liquid-to-solid ratio (mL / g) is 4:1), and the mixture is stirred and reacted at 60℃ for 60min. After the reaction, the mixture is separated into liquid and solid phases using a centrifuge to obtain filter residue with a water content of 12.8wt%. The filter residue is then evenly mixed with 200g of anthracite coal, the amount of which is 20% of the weight of the hematite slag. The mixed products were heated to 1050℃ in a tubular furnace using coal gas combustion for 3 hours, with the oxygen concentration in the flue gas controlled to be less than 6.0% at the end of the reaction. The reaction products were then rapidly cooled using nitrogen blast and finely ground to a particle size of ≤74μm. They were then magnetically separated twice under a magnetic field strength of 1800 Oe. The resulting iron concentrate, obtained from the two magnetic separations, contained, by mass percentage, 87.6% iron, 0.01% zinc, 0.22% copper, 0.05% nickel, 0.02% cobalt, 0.08% cadmium, 0.01% lead, 0.005% arsenic, 0.98% sulfur, and 0.01% phosphorus, with the remainder being oxygen and trace amounts of carbon.

[0059] The iron recovery rate was 98.5%.

[0060] Comparative Example 1

[0061] Other conditions were the same as in Examples 1-1, except for the reduction and impurity removal reaction temperature. The mixed product was heated to 800°C in a tubular furnace using coal gas combustion, and the reaction time was 3 hours. The obtained magnetic separation product, iron concentrate, contained, by mass percentage, 73.2% iron, 0.65% zinc, 0.11% copper, 0.10% nickel, 0.01% cobalt, 0.10% cadmium, 0.18% lead, 0.10% arsenic, 3.0% sulfur, and 0.10% phosphorus, with the remainder being oxygen and carbon. Lowering the reduction and impurity removal reaction temperature resulted in poorer impurity removal, insufficient iron reduction conditions, and a deterioration in the quality of the iron concentrate.

[0062] Comparative Example 2

[0063] The other conditions are the same as in Example 1-1, except that no coke powder or other carbonaceous reducing agents are added; only carbon monoxide from the coal gas is used for reduction. The resulting magnetic separation product, iron concentrate, contains, by mass percentage, 70.2% iron, 0.42% zinc, 0.01% copper, 0.02% nickel, 0.01% cobalt, 0.08% cadmium, 0.09% lead, 0.07% arsenic, 1.85% sulfur, and 0.05% phosphorus, with the remainder being oxygen and carbon. Iron concentrate can be obtained without adding coke powder or other reducing agents, but the quality of the iron concentrate is lower than that obtained with coke powder.

[0064] Comparative Example 3

[0065] Other conditions were the same as in Example 1-1, except for the reduction and impurity removal reaction time, which was shortened to 1 hour. The resulting magnetic separation product, iron concentrate, contained, by mass percentage, 70.5% iron, 0.65% zinc, 0.02% copper, 0.07% nickel, 0.06% cobalt, 0.10% cadmium, 0.10% lead, 0.1% arsenic, 1.85% sulfur, and 0.08% phosphorus, with the remainder being oxygen and carbon. At this point, the iron content in the product was too low and the sulfur content too high.

[0066] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for preparing iron concentrate from hematite slag using hydrometallurgical methods, characterized in that: The hematite slag produced by hydrometallurgy is purified by dilute sulfuric acid solution, washed and filtered, and then mixed with a carbonaceous reducing agent. Coal gas is introduced into the mixture for combustion, and the reaction temperature is ensured to be greater than or equal to 800°C. The reaction is carried out for at least 1 hour. After the reaction is completed, the mixture is rapidly cooled, finely ground and magnetically separated to obtain iron concentrate. The concentration of the dilute sulfuric acid is 10 g / L to 50 g / L, and the liquid-solid ratio of the dilute sulfuric acid solution to the hematite slag is 2 to 5:1 in mL:g.

2. The method for preparing iron concentrate from hematite slag in hydrometallurgical processes according to claim 1, characterized in that: Includes the following steps; (1) Acid dissolution and impurity removal of hematite slag: The hematite slag from hydrometallurgical process is reacted with a dilute sulfuric acid solution with a sulfuric acid concentration of 10 g / L ~ 50 g / L for acid dissolution and impurity removal. After the reaction is completed, the liquid and solid are separated to obtain filter residue with a water content of 8wt%~15wt%. (2) Mixing: Mix the filter residue produced in step (1) with carbonaceous reducing agent. The proportion of carbonaceous reducing agent is 0-25% of the weight of the filter residue. (3) Reduction and purification: Gas is introduced into the mixture produced in step (2) and combustion is carried out while ensuring that the reaction temperature is 800℃~1350℃. The reaction is carried out for 1h~4h to reduce and remove impurities. After the reaction is completed, the mixture is cooled down. (4) Fine grinding and magnetic separation: The product of step (3) is finely ground and magnetically separated to obtain high-quality iron concentrate.

3. The method for preparing iron concentrate from hematite slag in hydrometallurgical processes according to claim 2, characterized in that: The hydrometallurgical hematite slag comprises, by mass percentage: Fe 45%~65%, Zn 1%~5%, and S 2%~10%.

4. The method for preparing iron concentrate from hematite slag in hydrometallurgical processes according to claim 2, characterized in that: In step (1), the particle size of the hematite slag is ≤74 micrometers.

5. The method for preparing iron concentrate from hematite slag in hydrometallurgical processes according to claim 2, characterized in that: In step (1), after removing impurities with dilute sulfuric acid solution, the washing temperature is controlled at 40℃~80℃ and the washing time is 20 min~60 min.

6. The method for preparing iron concentrate from hematite slag in hydrometallurgical processes according to claim 2, characterized in that: The carbonaceous reducing agent used in step (2) is one or more of coke powder, anthracite, coking coal, and reducing coal, and its addition amount is 0 to 25% of the weight of hematite slag.

7. The method for preparing iron concentrate from hematite slag in hydrometallurgical processes according to claim 2, characterized in that: The reaction time for the reduction and impurity removal in step (3) is 1h to 4h, and the oxygen concentration in the flue gas at the reaction endpoint is controlled to be below 10v.

8. The method for preparing iron concentrate from hematite slag in hydrometallurgical process according to claim 2, characterized in that: Step (3) Fine grinding process: The particle size of the material is ≤74μm, and the magnetic field strength of the magnetic separation process is 800~2000 Oe.

9. A method for preparing iron concentrate from hematite slag in hydrometallurgical processes according to any one of claims 1-6, characterized in that: The produced iron concentrate contains ≥70% iron, ≤0.5% zinc, ≤0.1% copper, ≤0.1% nickel, ≤0.1% cobalt, ≤0.1% cadmium, ≤0.1% lead, ≤0.1% arsenic, ≤3.0% sulfur, and ≤0.05% phosphorus.