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

Abstract

The invention relates to a method for preparing fine iron powder by removing impurities from hematite slag in hydrometallurgy, and belongs to the technical field of chemical metallurgy. The method comprises the following steps: carrying out acid dissolution, impurity removal, washing and filtration on hematite slag produced in a hydrometallurgy process, mixing the hematite slag with a carbonaceous reducing agent, heating the mixed product to 800-1350 DEG C by adopting gas combustion, carrying out heat preservation reaction for 1-4 hours, and after the reaction is finished, carrying out rapid cooling, fine grinding and magnetic separation to obtain the high-purity hematite slag. The iron fine powder contains 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 method has the advantages that the residual impurities of the hematite slag can be deeply removed, the high-quality fine iron powder is obtained, the resource utilization rate of the hematite slag is high, the impurity removal efficiency is good, and the quality of the fine iron powder is good.

Description

Technical Field

[0001] The invention relates to a method for preparing iron concentrate by removing impurities from hydrometallurgical hematite slag, belonging to the technical field of chemical metallurgy. Background Art

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

[0003] In order to solve the problem of separation and precipitation of iron in iron-containing solution in hydrometallurgical process, domestic and foreign scientific and technological workers have carried out extensive research and successively developed iron removal methods such as hydrolysis, potassium iron alum, goethite and hematite, which have better achieved the separation of non-ferrous metals such as zinc, nickel, copper, cobalt, cadmium, indium, germanium and iron in the leachate, reduced the output of iron slag to a certain extent, and reduced the loss of valuable metals such as zinc, nickel, cobalt, copper, lead, cadmium, indium, germanium in iron-containing waste slag, increased the recovery rate of valuable metals, and promoted the progress and development of hydrometallurgical process technology. Among them, hematite iron removal is to precipitate and separate ferrous sulfate in sulfate solution containing zinc sulfate, nickel sulfate and other sulfates in the form of hematite. Compared with other iron removal methods, hematite iron removal has the advantages of high iron content of iron precipitation products, high precipitation efficiency, and good crystallization and filtration performance of precipitates, and has become one of the main technologies for hydrometallurgical iron removal. However, in actual production, the hematite slag produced by the hydrometallurgical solution hematite ore method for removing iron still contains high levels of heavy metal ions and impurity elements such as zinc, copper, cadmium, lead, arsenic, and sulfur, making it difficult to directly utilize the hematite slag as a high-value resource, and there is a risk of environmental pollution during the storage process.

[0004] Therefore, how to deeply remove heavy metal ions and impurity elements from the hematite slag produced by the hydrometallurgical hematite removal process, reduce the heavy metal content, improve the quality of iron-containing products, and expand the application field is a technical problem that needs to be studied and solved. Summary of the invention

[0005] In view of the high content of heavy metal impurities in hydrometallurgical hematite slag and the difficulty in resource utilization, the present invention provides a method for removing impurities from hydrometallurgical hematite slag to prepare iron concentrate. The method uses methods such as acid dissolution pre-impurity removal of hematite slag, high-temperature reduction deep impurity removal, removal of bound oxygen, magnetic separation, etc. to remove impurity components such as zinc sulfate, copper sulfate, lead sulfate, arsenate, basic iron sulfate, and cadmium-containing sulfate in the hematite slag in steps and in depth. At the same time, under high-temperature reduction conditions, part of the bound oxygen of volatile impurity elements is reduced and removed, crystal water is removed, the heavy metal content in the hematite slag is reduced, the purity of iron compounds is improved, the reaction product is cooled, finely ground, and magnetically separated to produce high-quality iron concentrate, thereby expanding the resource utilization of hematite slag.

[0006] The invention discloses a method for preparing iron ore concentrate by removing impurities from hydrometallurgical hematite slag. The method comprises the following specific operations: removing impurities from the hematite slag produced by hydrometallurgy by using a dilute sulfuric acid solution, washing and filtering the hematite slag, mixing the hematite slag with a carbonaceous reducing agent, introducing coal gas into the mixed product for combustion and ensuring that the reaction temperature is greater than or equal to 800 DEG C, reacting for at least 1 hour, rapidly cooling after the reaction, fine grinding, and magnetic separation to obtain the iron ore concentrate, wherein the concentration of the dilute acid is 10 g / L-50 g / L, and the liquid-solid ratio of the dilute sulfuric acid solution to the hematite slag is 2-5:1, preferably 3-5:1, in terms of mL:g.

[0007] As a preferred embodiment, the present invention provides a method for preparing iron ore concentrate by removing impurities from hydrometallurgical hematite slag, comprising the following steps:

[0008] (1) Acid dissolution and impurity removal of hematite slag: The hydrometallurgical hematite slag is subjected to acid dissolution and impurity removal using a sulfuric acid solution with a concentration of 10 g / L to 50 g / L, preferably 10 to 20 g / L. After the reaction is completed, liquid-solid separation is performed to obtain a filter residue containing 8 wt% to 15 wt% of water.

[0009] (2) Mixing: mixing the filter residue produced in step (1) with a carbonaceous reducing agent, wherein the ratio of the carbonaceous reducing agent is 0-25% by weight of the filter residue, preferably 5%-21% by weight, and more preferably 10-21% by weight;

[0010] (3) Reduction and impurity removal: introducing coal gas into the mixture produced in step (2) for combustion and ensuring that the reaction temperature is 800-1350°C, preferably 800-1200°C, for 1h-4h to carry out reduction and deep impurity removal, and cooling after the reaction is completed;

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

[0012] In the present invention, 10 g / L ~ 50g / L is selected and the liquid-solid ratio of the dilute sulfuric acid solution to the hematite slag is controlled to be 2~5:1 in terms of mL:g; this is because: under this condition, the reaction degree of the dilute acid (including dilute sulfuric acid) with the iron oxide is relatively weak, and the dissolution ratio of the iron oxide is small, but at this time the dilute acid has a strong impurity removal ability and can dissolve the zinc sulfate, basic sulfate, hydroxide, etc. in the hematite, which ensures the depth of impurity removal and the effective recovery rate of iron resources to a certain extent. On this basis, further optimization is carried out. With the cooperation of various parameters, the iron recovery rate and the iron content in the obtained product can be improved (such as the iron content can be greater than 85% and the iron recovery rate can be greater than 94% through two magnetic separations). Of course, at this time, the particle size parameters of the hematite slag are combined to further remove impurities. Therefore:

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

[0014] The hydrometallurgical hematite slag of the present invention includes: hematite slag produced by the iron ore precipitation process of the iron-containing solution produced by the hydrometallurgical process of zinc, nickel, cobalt, copper and other metals, which contains, by mass percentage: Fe 45%~65%, Zn 1%~5%, S2%~10%. As a further preferred, its main chemical composition (wt%) is: Fe 45%~65%, Zn 1%~5%, S 2%~10%, Cu≤1%, Ni content≤1.0%, Co content≤1.0%.

[0015] In the present invention, in step (1), 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 preliminary impurity removal.

[0016] In the present invention, in step (1), the water content of the filter residue is controlled to be 10wt% to 20wt%, so that the hematite slag and the carbonaceous reducing agent can be fully mixed and uniformly mixed, thereby improving the reduction effect, avoiding dust flying, and improving the environment. The subsequent introduction of coal gas can reduce the iron oxide in the hematite slag to low-valent iron.

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

[0018] In the present invention, in step (3), the reduction temperature is preferably 900°C to 1200°C, more preferably 1000°C to 1200°C, and even more preferably 1000°C to 1080°C because: too low a temperature will result in low removal efficiency of impurity components such as zinc and sulfur, and poor quality of iron concentrate; too high a temperature will result in excessive energy consumption and agglomeration of the reaction product. The reaction time is controlled to be 1h to 4h because: if the reaction time is too short, the reaction is not sufficient, the removal efficiency of impurities such as zinc and sulfur is poor, and if the reaction time is too long, the production efficiency is low and the energy consumption is high.

[0019] When used in industry, it is also necessary to control the oxygen concentration in the flue gas at the end of the reaction to be lower than 10v%.

[0020] Optimally, the fine grinding process in step (4) controls the particle size of the finely ground material to be ≤74 μm, and the magnetic field strength of the magnetic separation process to be 800-2000 Oe.

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

[0022] The beneficial effects of the present invention are:

[0023] (1) The present invention can efficiently remove various heavy metals such as zinc, copper, nickel, cobalt, lead, arsenic, cadmium and impurity elements such as sulfur and phosphorus from hydrometallurgical hematite slag containing zinc, nickel, cobalt and copper, and at the same time reduce the bound oxygen in the hematite slag, increase the iron content, produce high-quality iron concentrate, and realize the resource utilization of hematite slag.

[0024] (2) The present invention adopts a combination of various technical means such as acid dissolution and impurity removal, high-temperature reduction and impurity removal, and magnetic separation to achieve the step-by-step removal of heavy metals and impurity elements in different phases such as sulfates such as zinc, copper, nickel, cobalt, and cadmium, basic iron 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 such as those that are difficult to dissolve and volatilize in hematite slag, and has a high efficiency in the synergistic removal of heavy metals and impurity elements such as phosphorus and sulfur.

[0025] (3) The technology of the present invention has good impurity removal effect, low iron loss rate, high iron recovery rate and high iron resource utilization rate.

[0026] (4) The iron ore concentrate produced by the scheme of the present invention is of high quality, which is better than the relevant industry standard index requirements of the iron ore concentrate produced as a by-product of non-ferrous metal smelting. After optimization, the iron content of the iron ore concentrate produced is ≥85%, the zinc content is ≤0.5%, the copper content is ≤0.1%, the nickel content is ≤0.1%, the cobalt content is ≤0.1%, the cadmium content is ≤0.1%, the lead content is ≤0.1%, the arsenic content is ≤0.1%, the sulfur content is ≤1.5%, and the phosphorus content is ≤0.05%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a SEM image of the iron ore concentrate prepared in Example 1;

[0028] from Figure 1It can be seen that the particle size distribution of the iron powder prepared by the present invention is relatively uniform, and the specific surface area is large, and the obtained particles are obviously in a secondary particle state. DETAILED DESCRIPTION

[0029] The present invention will be further described below in conjunction with specific implementation modes.

[0030] Example 1-1

[0031] A method for preparing iron concentrate from hydrometallurgical hematite slag by removing impurities, wherein the specific operation is as follows: 1000g of hematite slag produced by hydrometallurgical zinc smelting is taken, and the chemical composition (wt%) thereof is: 57.0% iron content, 1.5% zinc content, 0.15% copper content, 0.11% nickel content, 0.02% cobalt content, 0.15% cadmium content, 0.20% lead content, 0.18% arsenic content, 4.5% sulfur content, 0.10% phosphorus content, and the rest is oxygen. 3000mL of sulfuric acid solution with a sulfuric acid concentration of 20g / L (liquid-to-solid ratio (mL / g) is 3:1) is added, and the mixture is stirred and reacted at 60°C for 30min. After the reaction is completed, a centrifuge is used for liquid-solid separation to obtain a filter residue containing 12wt% water. The filter residue is evenly mixed with 100g of coke powder, and the amount of coke powder added is 10% of the weight of the hematite slag. The mixed product was heated to 1000°C in a tube furnace by direct combustion of coal gas (coal gas directly contacts the mixed product), the reaction time was 2h, and the oxygen concentration in the flue gas at the end of the reaction was controlled to be 5%. The reaction product was quickly cooled and finely ground to a material particle size of ≤74μm, and magnetically separated twice under a magnetic field strength of 800 Oe. Among them, the product obtained by the first magnetic separation had an iron content of 76.0%, a zinc content of 0.30%, a copper content of 0.05%, a nickel content of 0.02%, a cobalt content of 0.01%, a cadmium content of 0.05%, a lead content of 0.03%, an arsenic content of 0.05%, a sulfur content of 1.25%, and a phosphorus content of 0.01%, by mass percentage. The iron concentrate obtained by two magnetic separations 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, 0.01% phosphorus, and the rest is oxygen and trace carbon.

[0032] The recovery rate of iron was 95.6%.

[0033] Example 1-2

[0034] The raw materials used are the same as those in Example 1-1, except that the amount of coke powder added is 15% of the weight of the hematite slag; the iron concentrate obtained by two magnetic separations has, 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, 0.01% phosphorus, and the rest is oxygen and trace carbon.

[0035] The recovery rate of iron was 94.3%.

[0036] Examples 1-3

[0037] The raw materials used are the same as those in Example 1-1, except that: the mixed product is heated to 1350°C by gas combustion in a tubular furnace; the magnetic separation product iron concentrate obtained by two magnetic separations has, 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, 0.01% phosphorus, and the rest is oxygen and trace carbon.

[0038] The recovery rate of iron was 95.0%.

[0039] Examples 1-4

[0040] The raw materials used are the same as those in Example 1-1, except that: the mixed product is heated to 800°C by gas combustion in a tubular furnace; the magnetic separation product iron concentrate obtained by two magnetic separations has, 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, 0.06% phosphorus, and the rest are oxygen and carbon.

[0041] The recovery rate of iron was 94.2%.

[0042] Examples 1-5

[0043] The raw materials used are consistent with those in Example 1-1, except that: the mixed product is heated to 1000°C by gas combustion in a tubular furnace and kept warm for 3 hours; the magnetic separation product iron concentrate obtained by two magnetic separations has an iron content of 91.7%, a zinc content of 0.15%, a copper content of 0.01%, a nickel content of 0.01%, a cobalt content of 0.01%, a cadmium content of 0.01%, a lead content of 0.01%, an arsenic content of 0.01%, a sulfur content of 0.50%, a phosphorus content of 0.01%, and the rest is oxygen and trace carbon.

[0044] The recovery rate of iron was 94.2%.

[0045] Examples 1-6

[0046] The raw materials used were the same as those in Example 1-1, except that 4000 mL of a sulfuric acid solution having a sulfuric acid concentration of 50 g / L (liquid-to-solid ratio (mL / g) was 4:1) was added;

[0047] The iron concentrate obtained by two magnetic separations 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, 0.01% phosphorus, and the rest are oxygen and carbon.

[0048] The recovery rate of iron was 91.0%.

[0049] Example 2

[0050] A method for removing impurities from hydrometallurgical hematite slag to prepare iron concentrate, the specific operation of which is as follows: 1000g of hematite slag produced by hydrometallurgical zinc smelting is taken, and the chemical composition of the hematite slag is 55.0% iron content, 1.5% zinc content, 0.12% copper content, 0.10% nickel content, 0.03% cobalt content, 0.11% cadmium content, 0.21% lead content, 0.10% arsenic content, 3.2% sulfur content, and 0.10% phosphorus content. 4000mL of sulfuric acid solution with a sulfuric acid concentration of 30g / L (liquid-solid ratio (mL / g) is 4:1) is added, and the reaction is stirred at 40°C for 30min. After the reaction is completed, a centrifuge is used for liquid-solid separation to obtain a filter residue containing 10wt% water. Without adding a reducing agent such as coke powder, anthracite or high-quality coal, the mixed product is heated to 1200°C by coal gas combustion in a tubular furnace, the reaction time is 1h, and the oxygen concentration in the flue gas at the end of the reaction is controlled to be less than 5.0%. The reaction product is rapidly cooled by nitrogen blast and then finely ground to a particle size of ≤74 μm. It is magnetically separated twice under a magnetic field strength of 1200 Oe. The magnetic separation product iron concentrate obtained by the two magnetic separations has, 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, 0.02% phosphorus, and the rest is oxygen and trace carbon.

[0051] The recovery rate of iron was 96.5%.

[0052] Example 3

[0053] A method for removing impurities from hydrometallurgical hematite slag to prepare iron concentrate, the specific operation of which is as follows: 1000g of hematite slag produced by nickel hydrometallurgy, the chemical composition (wt%) of which is: 62.5% iron content, 0.01% zinc, 0.02% copper, 0.5% nickel, 0.04% cobalt, 0.01% cadmium, 0.01% lead, 0.08% arsenic, 3.0% sulfur, and 0.10% phosphorus. 4000mL of sulfuric acid solution with a sulfuric acid concentration of 40g / L (liquid-to-solid ratio (mL / g) is 4:1) is added, and the mixture is stirred and reacted at 40°C for 50min. After the reaction is completed, a centrifuge is used for liquid-solid separation to obtain a filter residue containing 8wt% water. The filter residue is evenly mixed with 150g of coke powder, and the amount of coke powder added is 15% of the weight of the hematite slag. The mixed product was heated to 900°C in a tube furnace by gas combustion, the reaction time was 3h, and the oxygen concentration in the flue gas at the end of the reaction was controlled to be less than 5.0%. The reaction product was quickly cooled by nitrogen blast and then finely ground to a material particle size of ≤74μm, and magnetically separated twice under a magnetic field strength of 1000 Oe. The iron concentrate obtained by the magnetic separation twice contained 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, 0.01% phosphorus, and the rest was oxygen and trace carbon.

[0054] The recovery rate of iron was 96.5%.

[0055] Example 4

[0056] A method for removing impurities from hydrometallurgical hematite slag to prepare iron concentrate, the specific operation of which is as follows: 1000g of hematite slag produced by cobalt hydrometallurgy is taken, and the chemical composition of the hematite slag is 58.0% iron content, 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 sulfuric acid solution with a sulfuric acid concentration of 50g / L (liquid-to-solid ratio (mL / g) is 3:1) is added, and the mixture is stirred and reacted at 80°C for 60min. After the reaction is completed, a centrifuge is used for liquid-solid separation to obtain a filter residue containing 15wt% water. The filter residue is evenly mixed with 150g of high-quality coal, and the amount of the added coal is 15% of the weight of the hematite slag. The mixed product was heated to 900°C in a tube furnace by gas combustion, the reaction time was 1.5h, and the oxygen concentration in the flue gas at the end of the reaction was controlled to be less than 3.5%. The reaction product was quickly cooled by nitrogen blast and then finely ground to a material particle size of ≤74μm, and magnetically separated twice under a magnetic field strength of 1500 Oe. The magnetic separation product iron concentrate obtained by the two magnetic separations contained 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, 0.01% phosphorus, and the rest was oxygen and trace carbon.

[0057] The recovery rate of iron was 96.2%.

[0058] Example 5

[0059] A method for removing impurities from hydrometallurgical hematite slag to prepare iron concentrate, the specific operation of which is as follows: 1000g of hematite slag produced by copper hydrometallurgy is taken, and the chemical composition of the hematite slag is 58.6% iron content, 0.01% zinc, 1.52% copper, 0.12% nickel, 0.10% cobalt, 0.12% cadmium, 0.10% lead, 0.15% arsenic, 3.8% sulfur, and 0.11% phosphorus. 4000mL of sulfuric acid solution with a sulfuric acid concentration of 10g / L (liquid-solid ratio (mL / g) is 4:1) is added, and the mixture is stirred at 60°C for 60min for reaction. After the reaction, a centrifuge is used for liquid-solid separation to obtain a filter residue containing 12.8wt% water. The filter residue is evenly mixed with 200g anthracite, and the amount of the added residue is 20% of the weight of the hematite slag. The mixed product was heated to 1050°C in a tube furnace by gas combustion, the reaction time was 3h, and the oxygen concentration in the flue gas at the end of the reaction was controlled to be less than 6.0%. The reaction product was quickly cooled by nitrogen blast and then finely ground to a material particle size of ≤74μm, and magnetically separated twice under a magnetic field strength of 1800 Oe. The iron concentrate obtained by the magnetic separation twice had an iron content of 87.6%, a zinc content of 0.01%, a copper content of 0.22%, a nickel content of 0.05%, a cobalt content of 0.02%, a cadmium content of 0.08%, a lead content of 0.01%, an arsenic content of 0.005%, a sulfur content of 0.98%, a phosphorus content of 0.01%, and the rest was oxygen and trace carbon.

[0060] The recovery rate of iron was 98.5%.

[0061] Comparative Example 1

[0062] Other conditions are consistent with Example 1-1, except that the reduction and impurity removal reaction temperature is different, and the mixed product is heated to 800°C in a tube furnace by gas combustion, and the reaction time is 3h. In the obtained magnetic separation product iron concentrate, by mass percentage, the iron content is 73.2%, zinc content is 0.65%, copper content is 0.11%, nickel content is 0.10%, cobalt content is 0.01%, cadmium content is 0.10%, lead content is 0.18%, arsenic content is 0.10%, sulfur content is 3.0%, phosphorus content is 0.10%, and the rest is oxygen and carbon. Lowering the reduction and impurity removal reaction temperature reduces, the impurity removal effect deteriorates, the iron reduction conditions are insufficient, and the quality of the iron concentrate deteriorates.

[0063] Comparative Example 2

[0064] Other conditions are consistent with those of Example 1-1, except that coke powder and other carbonaceous reducing agents are not added, and only carbon monoxide in coal gas is used for reduction. The iron concentrate obtained by magnetic separation has an iron content of 70.2%, a zinc content of 0.42%, a copper content of 0.01%, a nickel content of 0.02%, a cobalt content of 0.01%, a cadmium content of 0.08%, a lead content of 0.09%, an arsenic content of 0.07%, a sulfur content of 1.85%, a phosphorus content of 0.05%, and the rest is oxygen and carbon. Iron concentrate can also be obtained without adding coke powder and other reducing agents, but the quality of the iron concentrate is lower than that of the one with coke powder.

[0065] Comparative Example 3

[0066] The other conditions are consistent with those of Example 1-1, except that the reduction and impurity removal reaction time is shortened to 1 h, and the magnetic separation product iron concentrate obtained has an iron content of 70.5%, a zinc content of 0.65%, a copper content of 0.02%, a nickel content of 0.07%, a cobalt content of 0.06%, a cadmium content of 0.10%, a lead content of 0.10%, an arsenic content of 0.1%, a sulfur content of 1.85%, a phosphorus content of 0.08%, and the rest is oxygen and carbon. At this point, the iron content in the product is low and the sulfur content is too high.

[0067] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing iron concentrate by removing impurities from hydrometallurgical hematite slag, characterized in that: The hematite slag produced by hydrometallurgy is removed from impurities with a dilute sulfuric acid solution, washed and filtered, and then mixed with a carbonaceous reducing agent. Coal gas is introduced into the mixed product 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 temperature is quickly cooled, finely ground, and magnetically separated to obtain iron ore concentrate. The concentration of the dilute sulfuric acid is 10g / L~50g / L, and the liquid-to-solid ratio of the dilute sulfuric acid solution to the hematite slag is 2~5:1 in mL:g.

2. The method for preparing iron concentrate by removing impurities from hydrometallurgical hematite slag according to claim 1, characterized in that: The method comprises the following steps: (1) Acid dissolution and impurity removal of hematite slag: The hydrometallurgical hematite slag is subjected to acid dissolution and impurity removal using a dilute sulfuric acid solution with a sulfuric acid concentration of 10 g / L to 50 g / L. After the reaction is completed, liquid-solid separation is performed to obtain a filter residue containing 8 wt% to 15 wt% of water; (2) Mixing: mixing the filter residue produced in step (1) with a carbonaceous reducing agent, wherein the ratio of the carbonaceous reducing agent is 0-25% of the weight of the filter residue; (3) Reduction and impurity removal: introducing coal gas into the mixture produced in step (2) for combustion and ensuring that the reaction temperature is 800°C to 1350°C, reacting for 1h to 4h to carry out reduction and deep impurity removal, and cooling after the reaction is completed; (4) Fine grinding and magnetic separation: The product of step (3) is finely ground and magnetically separated to obtain high-quality iron ore concentrate.

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

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

5. The method for preparing iron ore concentrate by removing impurities from hydrometallurgical hematite slag according to claim 2, characterized in that: After the impurities are removed by dilute sulfuric acid solution in step (1), the washing temperature is controlled to be 40°C to 80°C and the washing time is 20 min to 60 min.

6. The method for preparing iron ore concentrate by removing impurities from hydrometallurgical hematite slag 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 reduced coal, and the added amount thereof is 0-25% of the weight of the hematite slag.

7. The method for preparing iron ore concentrate by removing impurities from hydrometallurgical hematite slag according to claim 2, characterized in that: The reaction time of reduction and impurity removal in step (3) is 1 h to 4 h, and the oxygen concentration in the flue gas at the end of the reaction is controlled to be lower than 10 v%.

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

9. The method for preparing iron ore concentrate by removing impurities from hydrometallurgical hematite slag according to any one of claims 1 to 6, characterized in that: The iron content of the produced iron ore concentrate is ≥70%, 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 ≤3.0%, and phosphorus content ≤0.05%.

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