A method for improving the process of removing iron by hematite method

Abstract

This invention relates to an improved process for iron removal from hematite, comprising the following steps: S1 Pre-neutralization: The oxygen-pressurized liquid is neutralized with zinc calcined sand, and after sedimentation, neutralized liquid and neutralized slag are obtained separately; S2 Hematite iron removal: The neutralized liquid is used as the pre-iron removal liquid and enters the oxygen pressurization vessel, while pressurized gas is introduced, and then iron removal is performed. After filtration, iron-removed liquid and iron-removed slag are obtained separately; The iron-removed liquid is returned to the intermediate leaching process; The iron-removed slag is dried to constant weight to obtain hematite slag. This invention achieves resource utilization of iron slag through specific process conditions and treatment, reducing slag storage pressure while minimizing environmental impact.

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, and in particular to an improved process for iron removal from hematite. Background Technology

[0002] Most domestic hydrometallurgical zinc smelting enterprises use a fluidized bed roasting-two-stage leaching-potassium (sodium) alum process for iron removal-antimony salt purification for zinc concentrate processing and purification. Although the "alum process" has promoted the development of the zinc smelting industry, the potassium alum iron precipitation process itself has disadvantages such as large slag volume, premature iron curing, and mixing of hot acid leaching slag and alum slag, resulting in high slag treatment costs and preventing the resource utilization of iron. This iron precipitation process not only fails to effectively separate lead-silver slag and iron slag, but also introduces a large amount of sodium salt into the system. High sodium content in the system reduces the current efficiency of the zinc electrowinning process, and the addition of sodium salt also increases production costs. Furthermore, this smelting system also suffers from the presence of Fe in the solution during the hot acid leaching process. 3+ It reacts with PbSO4 to form PbFe6(SO4)4(OH) 12 This results in high iron content and large slag volume in the lead-silver slag, with no effective separation of lead and silver from iron. The resulting iron alum slag has little application value, and currently, all production enterprises can only stockpile it, posing a significant environmental risk. As national environmental protection requirements become more stringent and low-iron, high-quality resources are drastically reduced, the iron alum process can no longer meet the requirements of circular economy development.

[0003] Therefore, developing a method to utilize iron in zinc concentrate as a resource not only solves the environmental pollution and investment costs of iron slag storage, but also has great significance for improving the core competitiveness of the entire hydrometallurgical zinc smelting process, reducing environmental pollution risks, achieving clean production throughout the entire hydrometallurgical zinc smelting process, and promoting the circular economy development of the industry. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide an improved process for iron removal from hematite that is environmentally friendly and reduces slag volume.

[0005] To solve the above problems, the present invention provides an improved process for iron removal from hematite, comprising the following steps: S1 pre-neutralization: The oxygen-pressed liquid was neutralized with zinc calcined sand to pH 1.5-2.0, and after sedimentation, neutralized liquid and neutralized residue were obtained respectively; the neutralized residue was returned to the intermediate leaching process. Iron removal from S2 hematite: The neutralized liquid is introduced into the oxygen pressure vessel as the pre-iron removal liquid, and pressurized gas is introduced at the same time. Then, the neutralized liquid is subjected to iron removal. After filtration, iron removal liquid and iron removal slag are obtained respectively. The iron removal liquid is returned to the intermediate leaching process. The iron removal slag is dried to constant weight to obtain hematite slag.

[0006] The oxygen-pressurized liquid in step S1 is obtained by the following method: S11 raw material pretreatment: Zinc calcined sand was pretreated by leaching in concentrated sulfuric acid at a liquid-to-solid volume ratio of 4:1, with an endpoint pH of 4.8-5.2 and a treatment time of 1 hour. After sedimentation, supernatant and leaching underflow were obtained. The supernatant was then introduced into the system purification process. S12 oxygen pressure leaching: Concentrated sulfuric acid and water are added to the intermediate leaching bottom stream, and pressurized gas O2 is introduced simultaneously. Oxygen pressure leaching is carried out in an oxygen pressure vessel. The volume ratio of intermediate leaching bottom stream to concentrated sulfuric acid is 3~4:1, the volume ratio of intermediate leaching bottom stream to water is 1:1.5~2, the temperature is 110~135℃, the total pressure is 0.2~0.6MPa, the oxygen partial pressure is 0.2~0.23MPa, and the time is 1~3h, thus obtaining the oxygen pressure leaching solution. S13 performs solid-liquid separation on the oxygen pressure leaching solution to obtain oxygen pressure post-leaching liquid and oxygen pressure leaching residue. The oxygen pressure leaching residue is dried to constant weight to obtain lead-silver slag.

[0007] The pressurized gas in step S2 is O2.

[0008] In step S2, the pressurized gas is replaced by the pressure generated inside the oxygen pressure vessel.

[0009] The conditions for iron removal in step S2 are: neutralization liquid temperature of 185~200℃, total pressure of 1.1~1.5MPa, and time of 2~6h.

[0010] Compared with the prior art, the present invention has the following advantages: 1. Waste reduction and environmental protection: This invention enables the comprehensive utilization of iron resources through the iron removal process of hematite. The iron content of hematite slag is higher than that of iron alum slag, avoiding the problem that iron alum slag and lead-silver slag cannot be completely separated. After iron removal from hematite, the amount of iron slag is reduced from 25% to 20%, reducing the pressure on environmental protection.

[0011] 2. Compared with the potassium ferrous sulfate process, the hematite process of this invention is a non-ferrous sulfate iron removal process. The iron grade of the produced iron removal slag is high, which can realize the resource utilization of iron removal slag, reduce or eliminate environmental pollution, and has broad market prospects.

[0012] 3. Compared to traditional hematite iron removal processes, reducing the iron content of hematite before iron removal reduces Fe... 3+ Reduced to Fe 2+ Then it is slowly oxidized into hematite. In this invention, iron is removed directly from hematite before oxygen pressure iron removal without reduction, and hematite is generated.

[0013] 4. Significant economic benefits: Using the method of this invention, a smelter in Northwest China can produce 80,000 tons of hematite annually, which is worth 16 million yuan at 200 yuan / ton.

[0014] 5. The process of this invention is simple and easy to operate, reducing most of the labor costs. Furthermore, it produces no highly toxic waste liquid, waste residue, or waste gas emissions. Attached Figure Description

[0015] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0016] Figure 1 This is a flowchart of the present invention.

[0017] Figure 2 The image shows the XRD pattern of iron slag C1 in Example 1 of this invention.

[0018] Figure 3 The image shows the XRD pattern of iron slag C2 in Example 1 of this invention.

[0019] Figure 4 The image shows the XRD pattern of iron slag C3 in Example 1 of this invention.

[0020] Figure 5 The image shows the XRD pattern of iron slag C4 in Example 1 of this invention.

[0021] Figure 6 The image shows the XRD pattern of iron slag C5 in Example 1 of this invention.

[0022] Figure 7 The image shows the XRD pattern of iron slag C6 in Example 1 of this invention.

[0023] Figure 8 The image shows the XRD pattern of iron slag C7 in Example 1 of this invention.

[0024] Figure 9 The image shows the XRD pattern of iron slag C8 in Example 1 of this invention.

[0025] Figure 10 The image shows the XRD pattern of iron slag C9 in Example 1 of this invention. Detailed Implementation

[0026] like Figure 1 As shown, an improved process for iron removal from hematite includes the following steps: S1 pre-neutralization: The oxygen-pressed liquid was neutralized with zinc calcined sand to pH 1.5-2.0, and after sedimentation, neutralized liquid and neutralized residue were obtained respectively; the neutralized residue was returned to the intermediate leaching process.

[0027] The oxygen-pressurized liquid is obtained as follows: S11 raw material pretreatment: Zinc calcined sand was pretreated by leaching in concentrated sulfuric acid at a liquid-to-solid volume ratio (L / kg) of 4:1, with an endpoint pH of 4.8-5.2 and a treatment time of 1 hour. Some zinc was leached out from the calcined sand, and the supernatant and intermediate leaching underflow were obtained by sedimentation. The supernatant entered the system purification process.

[0028] S12 oxygen pressure leaching: Concentrated sulfuric acid and water are added to the intermediate leaching bottom stream, while pressurized gas O2 is introduced simultaneously. Oxygen pressure leaching is carried out in an oxygen pressure vessel. The volume ratio (mL / mL) of the intermediate leaching bottom stream to concentrated sulfuric acid is 3~4:1, the volume ratio (mL / mL) of the intermediate leaching bottom stream to water is 1:1.5~2, the temperature is 110~135℃, the total pressure is 0.2~0.6MPa, the oxygen partial pressure is 0.2~0.23MPa, and the time is 1~3h, thus obtaining the oxygen pressure leaching solution.

[0029] S13 performs solid-liquid separation on the oxygen pressure leaching solution to obtain oxygen pressure post-leaching solution and oxygen pressure leaching residue. The oxygen pressure leaching residue is dried to constant weight to obtain lead-silver slag.

[0030] Iron removal from S2 hematite: The neutralized liquid, used as the pre-iron removal liquid, enters the oxygen pressure vessel while pressurized gas is introduced. Iron removal is then performed on the neutralized liquid at a temperature of 185–200°C, a total pressure of 1.1–1.5 MPa, and a time of 2–6 hours. After filtration, iron-removed liquid and iron-removed slag are obtained separately. The iron-removed liquid is returned to the intermediate leaching process; the iron-removed slag is dried to constant weight to obtain hematite slag.

[0031] The pressurized gas is O2, but the pressure generated inside the oxygen pressure vessel can also be used to achieve the same effect.

[0032] Example 1: Experimental study on iron removal after neutralization of oxygen pressure leaching solution in zinc roasted sand 1. Conduct orthogonal experiments according to Table 1: Table 1. Orthogonal experimental table for iron removal from hematite 2. Through orthogonal experiments and SPSSAU statistical analysis for range data processing, the optimal experimental conditions for the iron removal stage of hematite were: temperature 200℃, 6h, pH=2.0. The Fe grade was 54.74%, the Zn content was 0.43%, and the S content was 1.88%. The results are shown in Table 2.

[0033] Table 2 Results of Optimal Conditions in Orthogonal Experiments 3. Jade phase analysis was performed on the obtained iron slag, and the results were as follows: Figures 2-10 The XRD pattern shown is illustrated. From the figure, we can observe that: Figure 2Oxygen pressure leaching results in the lowest conversion rate. When the system acidity is too high, the reaction temperature is too low, or the holding time is insufficient, a large amount of ferric iron only hydrolyzes to form metastable basic ferric sulfate hydrate, without fully decomposing into hematite. The slag has high sulfur content and low iron purity; the high crystallinity of the basic ferric sulfate easily leads to poor slag filtration performance and difficulty in removing sulfur impurities, resulting in low resource utilization value.

[0034] Figure 3 and Figure 2 The phase types are completely identical; the main peak intensity of basic ferric sulfate is slightly higher than that of... Figure 2 Hematite and quartz peak strength and Figure 2 It is close. The sulfur impurity content is the highest, the slag contains a lot of soluble sulfates, and it is easy to produce acidic leachate when stored.

[0035] Figure 4 The oxygen pressure leaching conditions have been significantly optimized compared to Figure 3 As the temperature increases, a large amount of basic ferric sulfate hydrate undergoes deep hydrolysis, removing sulfate ions and water of crystallization to transform into hematite; leaching dissolution / separation is more thorough. The iron content of the slag increases significantly, while the sulfur content decreases markedly; without the interference of a large amount of quartz impurities, the integrity of hematite crystallization is improved.

[0036] Potassium ferric sulfate in Figure 5 The proportion of middle school students is 80%. Figure 6 The proportion of middle school students was 10.99%. Figure 7 The proportion of middle-class was 17.92%. Figure 8 It accounts for 11.27%. Potassium ferruginum is an iron-containing sulfate mineral, and its formation is usually related to the oxidation and precipitation of iron-containing solutions under acidic conditions.

[0037] exist Figure 6 Hematite accounts for 89.01% of the total. Figure 7 The proportion of middle school students was 82.08%. Figure 8 The proportion of hematite in the slag is 88.73%. Hematite is a major iron-bearing mineral, but its presence in the slag at a certain proportion indicates that some hematite may not have been effectively recovered during the processing and has entered the slag phase.

[0038] Figure 9 Hematite exhibits strong peaks, with numerous and sharp characteristic peaks; basic ferric sulfate shows only sporadic and extremely weak peaks; no characteristic peaks of quartz are present. It has high iron content, the lowest sulfur content, good crystallinity, and few impurities.

[0039] Figure 10 Leaching conditions are relatively Figure 9 Slightly shortening the heat preservation time resulted in a small amount of incomplete conversion of the sulfur-iron mesophase, but the overall conversion level was good.

[0040] 4. The hematite method for iron removal involves the oxidation and hydrolysis of iron by oxygen under high temperature and pressure to produce Fe2O3. This method results in minimal iron slag and low zinc content, and is carried out in high-temperature and high-pressure equipment. The main reactions include: 4FeSO4+O2+2H2SO4=2Fe2(SO4)3+2H2O Fe₂(SO₄)₃ + 3H₂O = Fe₂O₃ + 3H₂SO₄ However, the iron in this experiment was not reduced in the early stage and was all ferric iron. It did not involve the process of ferrous iron being slowly oxidized to ferric iron. Based on the orthogonal experiment of hematite and the phase analysis of iron slag, it can be seen that when the iron content is relatively low, the proportion of silicon dioxide is relatively large, about 10%. In the process of transforming into hematite, some basic ferric sulfate hydrates will not be completely transformed, resulting in a low iron content in hematite.

[0041] Example 2 A method for improving the iron removal process from hematite includes the following steps: S1 pre-neutralization: 1300 mL of oxygen-pressed liquid was neutralized to pH 2.0 with zinc calcined sand. After sedimentation, 1100 mL of neutralized liquid and 50 g of neutralized residue were obtained. The neutralized residue was returned to the intermediate leaching process.

[0042] The oxygen-pressurized liquid is obtained as follows: S11 raw material pretreatment: 500g of zinc calcined sand was subjected to intermediate leaching pretreatment in 125mL of concentrated sulfuric acid, with an endpoint pH of 4.8 and a treatment time of 1h. Part of the zinc was leached out from the calcined sand, and after sedimentation, 1400mL of supernatant and 600mL of intermediate leaching underflow were obtained. The supernatant was then sent to the system purification process.

[0043] S12 oxygen pressure leaching: 160 mL of concentrated sulfuric acid was added to the bottom of the intermediate leaching solution, and water was added to bring the total volume to 1700 mL. At the same time, pressurized gas O2 was introduced, and oxygen pressure leaching was carried out in an oxygen pressure vessel at a temperature of 110℃, a total pressure of 0.26 MPa, an oxygen partial pressure of 0.20 MPa, and a time of 1 h, yielding 1600 mL of oxygen pressure leaching solution.

[0044] S13 performs solid-liquid separation on the oxygen pressure leaching solution to obtain 1500 mL of post-oxygen pressure leaching solution and oxygen pressure leaching residue. After drying the oxygen pressure leaching residue to constant weight, 43.6 g of lead-silver slag is obtained, with a slag rate of 8.72%.

[0045] Iron removal from S2 hematite: The neutralized liquid, used as the pre-iron removal liquid, entered the oxygen pressure vessel while pressurized gas O2 was introduced. Iron removal was then performed on the neutralized liquid at a temperature of 200℃, a total pressure of 1.1 MPa, and a time of 2 hours. After filtration, 850 mL of iron-removed liquid and iron-removed slag were obtained. The iron-removed liquid was returned to the intermediate leaching process. The iron-removed slag was dried to constant weight to obtain 29.4 g of hematite slag. The hematite slag contained 53.62% iron, 2.74% sulfur, and 0.44% zinc.

[0046] Example 3 A method for improving the iron removal process from hematite includes the following steps: S1 pre-neutralization: 1300 mL of oxygen-pressed liquid was neutralized to pH 2.0 with zinc calcined sand. After sedimentation, 1100 mL of neutralized liquid and 50 g of neutralized residue were obtained. The neutralized residue was returned to the intermediate leaching process.

[0047] Wherein: the oxygen-pressurized liquid is the same as in Example 2.

[0048] Iron removal from S2 hematite: The neutralized liquid, used as the pre-iron removal liquid, entered the oxygen pressure vessel while pressurized gas O2 was introduced. Iron removal was then performed on the neutralized liquid at a temperature of 185℃, a total pressure of 1.1 MPa, and a time of 4 hours. After filtration, 950 mL of iron-removed liquid and iron-removed slag were obtained. The iron-removed liquid was returned to the intermediate leaching process. The iron-removed slag was dried to constant weight to obtain 32.5 g of hematite slag. The hematite slag contained 54.74% iron, 2.98% sulfur, and 0.43% zinc.

[0049] Example 4 A method for improving the iron removal process from hematite includes the following steps: S1 pre-neutralization: 1300 mL of oxygen-pressed liquid was neutralized to pH 2.0 with zinc calcined sand. After sedimentation, 1100 mL of neutralized liquid and 50 g of neutralized residue were obtained. The neutralized residue was returned to the intermediate leaching process.

[0050] Wherein: the oxygen-pressurized liquid is the same as in Example 2.

[0051] Iron removal from S2 hematite: The neutralized liquid, used as the pre-iron removal liquid, enters the oxygen pressure vessel without the introduction of pressurized gas. The pressure vessel itself has a total pressure of 1.5 MPa. The neutralized liquid is then subjected to iron removal at 200℃ for 6 hours. After filtration, 850 mL of iron-removed liquid and iron-removed slag are obtained. The iron-removed liquid is returned to the intermediate leaching process. The iron-removed slag is dried to constant weight to obtain 29.8 g of hematite slag. The hematite slag contains 52.93% iron, 1.33% sulfur, and 0.43% zinc.

Claims

1. A method for improving the iron removal process from hematite, comprising the following steps: S1 pre-neutralization: The oxygen-pressed liquid was neutralized with zinc calcined sand to pH 1.5-2.0, and after sedimentation, neutralized liquid and neutralized residue were obtained respectively; the neutralized residue was returned to the intermediate leaching process. Iron removal from S2 hematite: The neutralized liquid is introduced into the oxygen pressure vessel as the pre-iron removal liquid, and pressurized gas is introduced at the same time. Then, the neutralized liquid is subjected to iron removal. After filtration, iron removal liquid and iron removal slag are obtained respectively. The iron removal liquid is returned to the intermediate leaching process. The iron removal slag is dried to constant weight to obtain hematite slag.

2. The method for improving the iron removal process from hematite as described in claim 1, characterized in that: The oxygen-pressurized liquid in step S1 is obtained by the following method: S11 raw material pretreatment: Zinc calcined sand was pretreated by leaching in concentrated sulfuric acid at a liquid-to-solid volume ratio of 4:1, with an endpoint pH of 4.8-5.2 and a treatment time of 1 hour. After sedimentation, supernatant and leaching underflow were obtained. The supernatant was then introduced into the system purification process. S12 oxygen pressure leaching: Concentrated sulfuric acid and water are added to the intermediate leaching bottom stream, and pressurized gas O2 is introduced simultaneously. Oxygen pressure leaching is carried out in an oxygen pressure vessel. The volume ratio of intermediate leaching bottom stream to concentrated sulfuric acid is 3~4:1, the volume ratio of intermediate leaching bottom stream to water is 1:1.5~2, the temperature is 110~135℃, the total pressure is 0.2~0.6MPa, the oxygen partial pressure is 0.2~0.23MPa, and the time is 1~3h, thus obtaining the oxygen pressure leaching solution. S13 performs solid-liquid separation on the oxygen pressure leaching solution to obtain oxygen pressure post-leaching liquid and oxygen pressure leaching residue. The oxygen pressure leaching residue is dried to constant weight to obtain lead-silver slag.

3. The method for improving the iron removal process from hematite as described in claim 1, characterized in that: The pressurized gas in step S2 is O2.

4. The method for improving the iron removal process from hematite as described in claim 1, characterized in that: In step S2, the pressurized gas is replaced by the pressure generated inside the oxygen pressure vessel.

5. The method for improving the iron removal process from hematite as described in claim 1, characterized in that: The conditions for iron removal in step S2 are: neutralization liquid temperature of 185~200℃, total pressure of 1.1~1.5MPa, and time of 2~6h.

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