Method for reducing zinc content of hazardous waste iron slag

Abstract

The application discloses a method for reducing the amount and zinc content of hazardous waste iron slag, and belongs to the technical field of hydrometallurgy. The method comprises the following steps: mixing and slurrying hazardous waste iron slag and mixed acid to obtain a mixed system, preheating the mixed system to obtain preheated slurry; stirring and reacting the preheated slurry and adjusting the pH; performing solid-liquid separation on the obtained mixture to obtain washed slag and washing liquid; and returning the washing liquid to other sections of a smelting system for slurry preparation or leaching, and returning the washed slag to a pyrometallurgical system. The method can realize the reduction of the amount and zinc content of hazardous waste iron slag under normal pressure and mild conditions, significantly simplifies the process flow, and greatly reduces the energy consumption compared with traditional zinc reduction technologies. The method not only effectively improves the reduction rate of the iron slag, but also has excellent zinc removal effect, and the residual zinc content in the washed slag is controlled at a low level, which helps to reduce the washing cost in the recovery process of iron-containing secondary resources (such as smelting iron slag).

Description

Technical Field

[0001] This invention relates to the field of hydrometallurgical technology, specifically to a method for reducing the amount of zinc in hazardous waste iron slag. Background Technology

[0002] In industries such as copper smelting, treating zinc-containing iron slag (typically containing approximately 15-30% Fe and 10% Zn) generated from secondary resources like flue dust is an important and challenging task. However, traditional iron slag treatment processes generally suffer from key drawbacks such as low zinc removal rates (usually below 70%) and low iron slag reduction rates. While conventional acid leaching can treat iron slag, achieving effective leaching often requires harsh high-temperature and high-pressure environments, resulting in significantly high energy consumption. More seriously, under these conditions, iron is prone to excessive dissolution, increasing not only the complexity and cost of subsequent iron removal processes but also reducing the purity of recovered zinc. Another commonly used technology, the iron alum process, can stabilize the iron slag structure to some extent, but the residual amount of water-soluble zinc after treatment remains high, and the subsequent solidification process is complex and lengthy, increasing the overall treatment cost.

[0003] These processes have serious limitations: on the one hand, the treated residue, due to its harmful components (such as residual zinc >6%) and the failure to effectively reduce its volume, is still classified as hazardous waste and must be disposed of by professional agencies, resulting in high annual disposal costs; on the other hand, high-value metals such as zinc are not fully recovered (low zinc recovery rate, serious loss of associated metals such as cadmium), causing a huge waste of scarce resources and directly increasing the overall operating costs of enterprises. Current processes struggle to achieve efficient zinc recovery from iron slag (high residual zinc content) and significant reduction in overall slag volume, which severely restricts the overall level of efficient and high-value resource recycling of hazardous waste iron slag.

[0004] Therefore, the industry urgently needs to develop an innovative iron slag treatment technology. Summary of the Invention

[0005] To address the issues of low zinc removal rate and low iron slag reduction rate in iron slag treatment processes, this invention provides a method for reducing the amount of hazardous waste iron slag and decreasing zinc content, specifically including the following steps: (1) Mix hazardous waste iron slag with mixed acid to form a slurry, and preheat the slurry to obtain a preheated slurry.

[0006] (2) The preheated slurry is stirred and reacted, and the pH is adjusted during the reaction. The mixture obtained from the reaction is separated into solid and liquid to obtain washing residue and washing liquid.

[0007] Preferably, in step (1) of the present invention, the mixed acid is prepared by mixing an acidic liquid and an aqueous system in a volume ratio of 1:1 to 10.

[0008] Preferably, the acidic liquid of the present invention is one or more of sulfuric acid, hydrochloric acid, acidic waste electrolyte, and smelting acidic liquid, and the water system is one or more of industrial production water (i.e., industrial tap water directly supplied to the plant area), distilled water, and industrial circulating water.

[0009] Preferably, the industrial production water described in this invention is circulating cooling water or process washing water generated during industrial production.

[0010] Preferably, the acidic waste electrolyte of the present invention refers to the acidic waste liquid generated during the zinc / copper electrolytic refining process; the smelting acidic liquid specifically refers to the dilute acid generated during the flue gas scrubbing process of pyrometallurgical smelting.

[0011] Preferably, in step (1) of the present invention, the solid-liquid ratio of hazardous waste iron slag to mixed acid is 1 kg: (1~10) L.

[0012] Preferably, the preheating condition in step (1) of the present invention is: preheating to 35~50℃.

[0013] Preferably, the conditions for the stirring reaction in step (2) of the present invention are: reaction temperature of 35~50℃, reaction time of 60~180 minutes, and stirring speed of 200~400 rpm.

[0014] Preferably, in step (2) of the present invention, the pH is adjusted to 1~2.

[0015] Preferably, the pH adjustment described in this invention can be achieved by mixing the acidic liquid and the water system described in this invention to prepare a mixed acid.

[0016] In step (2) of the present invention, the solid-liquid separation method can be a conventional method; preferably, the solid-liquid separation method of the present invention is plate pressure filtration, centrifugal separation, or membrane filtration.

[0017] This invention provides a method for reducing the amount of hazardous waste iron slag and decreasing zinc content, which has the following beneficial effects: (1) The present invention can achieve efficient treatment of hazardous waste iron slag under normal pressure and low temperature (35~50℃), which greatly reduces the pressure resistance requirements and energy consumption costs of the reaction equipment, significantly softens the process operation conditions, and has good economic efficiency and feasibility.

[0018] (2) The process flow of this invention is concise. It achieves both iron slag reduction and deep zinc removal in a single washing step, significantly simplifying the complex process of traditional zinc removal technology. After treatment by this invention, both the iron slag reduction rate and zinc removal rate are effectively improved, and the zinc residue in the washing slag is controlled at a low level. This not only achieves efficient recovery of valuable zinc, but also creates favorable conditions for the washing slag to be returned to the pyrometallurgical system as a qualified iron-containing raw material for resource utilization.

[0019] (3) This invention not only reduces the difficulty of treating hazardous waste iron slag and the subsequent disposal cost, but also significantly saves the washing cost in the recycling process of iron-containing secondary resources (such as lead, zinc and copper smelting iron slag), thus having both significant economic and environmental benefits. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the process for reducing the amount of hazardous waste iron slag and zinc content according to the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 The mixed acid used in this embodiment is composed of concentrated sulfuric acid and industrial production water mixed at a solid-liquid ratio of 1g:4mL. At the same time, a dilute sulfuric acid solution with a concentration of 40g / L is prepared using concentrated sulfuric acid and production water as a pH-adjusting acid solution. The hazardous waste iron slag treated in this embodiment contains 25.68% iron, 11.94% zinc, 0.13% arsenic, 0.6% copper, 0.01% indium (101.3g / t), and 11.07% sulfur.

[0023] A method for reducing the amount of zinc in hazardous waste iron slag is illustrated in the flowchart below. Figure 1 As shown, the specific steps include: (1) Mix hazardous waste iron slag and mixed acid at a solid-liquid ratio of 1kg:4L to form a slurry. Preheat the slurry to 40℃ to obtain a preheated slurry.

[0024] (2) The preheated slurry is stirred at 40°C for 60 minutes (stirring speed is 300 rpm), and the pH is adjusted to 1.5 using a prepared dilute sulfuric acid solution with a concentration of 40 g / L. After the reaction is completed, the slurry is filtered by plate press to obtain washing residue and washing liquid. The washing liquid obtained by this invention can be reused in other sections of the smelting system for slurry preparation, or the washing residue obtained from leaching can be treated by the reheating system.

[0025] In this embodiment, the zinc removal rate after treatment of hazardous waste iron slag was 79.3%; the amount of hazardous waste iron slag was reduced by 29.2%; the iron content of the washing liquid was 1.6 g / L; and the washing residue contained 29.1% iron and 3.36% zinc.

[0026] Example 2 The mixed acid used in this embodiment is composed of concentrated sulfuric acid and industrial production water mixed at a solid-liquid ratio of 1g:3mL. At the same time, a dilute sulfuric acid solution with a concentration of 40g / L is prepared using concentrated sulfuric acid and production water as a pH-adjusting acid solution. The hazardous waste iron slag treated in this embodiment contains 19.25% iron, 10.10% zinc, 0.11% arsenic, 0.9% copper, 0.01% indium (121.4g / t), and 12.16% sulfur.

[0027] A method for reducing the amount of zinc in hazardous waste iron slag specifically includes the following steps: (1) Mix hazardous waste iron slag and mixed acid at a solid-liquid ratio of 1kg:3L to form a slurry. Preheat the slurry to 45℃ to obtain a preheated slurry.

[0028] (2) The preheated slurry was stirred at 45°C for 120 minutes (stirring speed of 200 rpm), and the pH was adjusted to 2.0 using a prepared dilute sulfuric acid solution with a concentration of 40 g / L. After the reaction was completed, the slurry was filtered by plate press to obtain washing residue and washing liquid.

[0029] In this embodiment, the zinc removal rate after treatment of hazardous waste iron slag was 77.6%; the amount of hazardous waste iron slag was reduced by 32.2%; the iron content of the washing liquid was 1.0 g / L; and the washing residue contained 28.4% iron and 1.97% zinc.

[0030] Example 3 The mixed acid used in this embodiment is composed of concentrated sulfuric acid and industrial production water mixed at a solid-liquid ratio of 1g:3mL. At the same time, a dilute sulfuric acid solution with a concentration of 40g / L is prepared using concentrated sulfuric acid and production water as a pH-adjusting acid solution. The hazardous waste iron slag treated in this embodiment contains 28.68% iron, 13.94% zinc, 0.22% arsenic, 0.4% copper, 0.009% indium (93.2g / t), and 8.87% sulfur.

[0031] A method for reducing the amount of zinc in hazardous waste iron slag specifically includes the following steps: (1) Mix hazardous waste iron slag and mixed acid at a solid-liquid ratio of 1kg:2L to form a slurry. Preheat the slurry to 45℃ to obtain a preheated slurry.

[0032] (2) The preheated slurry was stirred at 45°C for 120 minutes (stirring speed of 200 rpm), and the pH was adjusted to 2.0 using a prepared dilute sulfuric acid solution with a concentration of 40 g / L. After the reaction was completed, the slurry was filtered by plate press to obtain washing residue and washing liquid.

[0033] In this embodiment, the zinc removal rate after treatment of hazardous waste iron slag was 78.3%; the amount of hazardous waste iron slag was reduced by 31.4%; the iron content of the washing liquid was 1.7 g / L; and the washing residue contained 28.5% iron and 2.31% zinc.

[0034] Example 4 The mixed acid used in this embodiment is composed of concentrated sulfuric acid and industrial production water mixed at a solid-liquid ratio of 1g:2mL. At the same time, a dilute sulfuric acid solution with a concentration of 40g / L is prepared using concentrated sulfuric acid and production water as a pH-adjusting acid solution. The hazardous waste iron slag treated in this embodiment contains 25.42% iron, 12.22% zinc, 0.31% arsenic, 0.2% copper, 0.01% indium (109.6g / t), and 12.87% sulfur.

[0035] A method for reducing the amount of zinc in hazardous waste iron slag specifically includes the following steps: (1) Mix hazardous waste iron slag and mixed acid at a solid-liquid ratio of 1kg:5L to form a slurry. Preheat the slurry to 40℃ to obtain a preheated slurry.

[0036] (2) The preheated slurry was stirred at 40°C for 90 minutes (stirring speed was 300 rpm), and the pH was adjusted to 1.5 using a prepared dilute sulfuric acid solution with a concentration of 40 g / L. After the reaction was completed, the slurry was filtered by plate pressure to obtain washing residue and washing liquid.

[0037] In this embodiment, the zinc removal rate after treatment of hazardous waste iron slag was 75.7%; the amount of hazardous waste iron slag was reduced by 29.5%; the iron content of the washing liquid was 1.2 g / L; and the washing residue contained 31.1% iron and 3.27% zinc.

[0038] Example 5 The mixed acid used in this embodiment is composed of concentrated sulfuric acid and industrial production water mixed at a solid-liquid ratio of 1g:7mL. At the same time, a dilute sulfuric acid solution with a concentration of 40g / L is prepared using concentrated sulfuric acid and production water as a pH-adjusting acid solution. The hazardous waste iron slag treated in this embodiment contains 22.63% iron, 12.23% zinc, 0.25% arsenic, 0.3% copper, 0.0099% indium (99.2g / t), and 10.31% sulfur.

[0039] A method for reducing the amount of zinc in hazardous waste iron slag specifically includes the following steps: (1) Mix hazardous waste iron slag and mixed acid at a solid-liquid ratio of 1kg:2L to form a slurry. Preheat the slurry to 40℃ to obtain a preheated slurry.

[0040] (2) The preheated slurry was stirred at 40°C for 180 minutes (stirring speed of 300 rpm), and the pH was adjusted to 1.0 using a prepared dilute sulfuric acid solution with a concentration of 40 g / L. After the reaction was completed, the slurry was filtered by plate press to obtain washing residue and washing liquid.

[0041] In this embodiment, the zinc removal rate after treatment of hazardous waste iron slag was 79.94%; the amount of hazardous waste iron slag was reduced by 30.3%; the iron content of the washing liquid was 1.8 g / L; and the washing residue contained 25.7% iron and 2.98% zinc.

[0042] Comparative Example 1 The difference between this comparative example and Example 1 is that the stirring reaction time in step (2) is shortened to 30 minutes, while the remaining steps are the same as in Example 1.

[0043] In this comparative example, the zinc removal rate after iron slag treatment was 56.41%, the reduction rate of hazardous waste iron slag was 29.7%, the iron content of the washing liquid was 1.52 g / L, and the washing residue contained 32.9% iron and 4.2% zinc.

[0044] Under the conditions of this comparative example, due to the short reaction time, the zinc-containing phase in the hazardous waste iron slag did not react sufficiently with the acid, resulting in a higher zinc residue in the washing residue and a slight decrease in the reduction effect. However, Example 1 used a reaction time of 60 minutes, which allowed for a more complete leaching reaction and thus a better treatment effect.

[0045] Comparative Example 2 The difference between this comparative example and Example 2 is that the reaction pH is adjusted to 2.5 in step (2), while the rest of the steps are the same as in Example 2.

[0046] In this comparative example, the zinc removal rate after iron slag treatment was 72.12%, the reduction rate of hazardous waste iron slag was about 29.0%, the iron content of the washing liquid was about 0.8 g / L, and the washing residue contained about 29.5% iron and about 4.8% zinc.

[0047] In this comparative example, the reaction system had a high pH and insufficient acidity, which was not conducive to the further leaching of zinc oxide and soluble zinc phase from the hazardous waste iron slag, resulting in an increase in zinc content and a decrease in zinc removal rate in the washing residue. Although the tendency of iron to dissolve is weakened under higher pH conditions, the overall reduction in amount and zinc is not as good as in Example 2. Therefore, a pH range of 1.0 to 2.0 can effectively balance zinc leaching effect and system stability.

[0048] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for reducing the amount of hazardous waste iron slag and decreasing zinc content, characterized in that, Specifically, the following steps are included: (1) Mix hazardous waste iron slag with mixed acid to form a slurry, and preheat the slurry to obtain a preheated slurry; (2) The preheated slurry is stirred and reacted, and the pH is adjusted during the reaction. The mixture obtained from the reaction is separated into solid and liquid to obtain washing residue and washing liquid.

2. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The mixed acid mentioned in step (1) is prepared by mixing an acidic liquid and a water system in a volume ratio of 1:1 to 10.

3. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 2, characterized in that, The acidic liquid is one or more of sulfuric acid, hydrochloric acid, acidic waste electrolyte, and smelting acidic liquid, and the water system is one or more of industrial production water, distilled water, and industrial circulating water.

4. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The solid-liquid ratio of the hazardous waste iron slag to the mixed acid in step (1) is 1 kg: (1~10) L.

5. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The preheating conditions described in step (1) are: preheat to 35~50℃.

6. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The conditions for the stirring reaction in step (2) are: reaction temperature of 35~50℃, reaction time of 60~180 minutes, and stirring speed of 200~400 rpm.

7. The method for reducing the amount of hazardous waste iron slag and decreasing zinc content according to claim 1, characterized in that, The pH is adjusted to 1-2 as described in step (2).

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