A method for removing zinc from zinc-containing blast furnace dust

Abstract

This invention discloses a method for removing zinc from zinc-containing blast furnace dust, comprising the following steps: mixing zinc-containing blast furnace dust with water, followed by crushing, dispersing, and slurry preparation to obtain a slurry; adding a flotation agent to the slurry for flotation to separate zinc and iron, obtaining a lean iron-rich zinc slurry and a rich iron-lean zinc slurry; adding the rich iron-lean zinc slurry to a vertical mill for scrubbing and grinding, followed by filtration to obtain ground solids; and sequentially subjecting the ground solids to preliminary crushing, drying, sieving, and air jet milling before conveying them to a hydrocyclone or air jet classifier for particle size classification to obtain rich zinc and rich iron-lean zinc materials. The method for removing zinc from zinc-containing blast furnace dust of this invention allows the recovered rich iron-lean zinc materials to be used as raw materials for blast furnace ironmaking, which has significant economic implications for the utilization of secondary resources of blast furnace dust.

Description

Technical Field

[0001] This invention relates to the field of secondary resource comprehensive recycling of blast furnace dust, specifically to a method for removing zinc from zinc-containing blast furnace dust. Background Technology

[0002] Blast furnace dust is a byproduct of blast furnace ironmaking. It consists of coarse particles carried out with blast furnace gas and obtained through gravity dust removal, followed by fine particles obtained through bag filter dust removal. The main mineral components of blast furnace dust are iron-bearing minerals and coke. The content of these two components varies slightly depending on the ironmaking raw materials and proportions. For steel companies, blast furnace dust is a suitable secondary resource for reuse as ironmaking raw material in the form of sintering feedstock. However, because blast furnace dust usually contains a high amount of zinc, and zinc is a major factor causing nodule formation inside the blast furnace and hindering stable operation, unstable blast furnace operation can result in economic losses of tens or even hundreds of millions of yuan. Therefore, deep dezincification of blast furnace dust before reuse is essential.

[0003] Chinese patent CN110743714B discloses a method for enriching and recovering zinc from blast furnace gas mud. This method uses flotation to remove zinc, and the zinc content of the dezincified zinc material is only about 2.4%. The zinc content of the dezincified product is relatively high for blast furnace ironmaking and is not suitable for use as a raw material for blast furnace ironmaking.

[0004] Therefore, developing a method to remove zinc from zinc-containing blast furnace dust and recover iron-rich materials that can be used as raw materials for blast furnace ironmaking is of great economic significance for the utilization of secondary resources of blast furnace dust. Summary of the Invention

[0005] The purpose of this invention is to provide a method for removing zinc from zinc-containing blast furnace dust. This method can obtain iron-rich and zinc-poor feedstock after zinc removal from zinc-containing blast furnace dust, which can be used as a raw material for blast furnace ironmaking and has significant economic benefits.

[0006] To achieve the above-mentioned objective, the present invention provides a method for removing zinc from zinc-containing blast furnace dust, comprising the following steps:

[0007] Step (1): After mixing zinc-containing blast furnace dust and water, the mixture is crushed, dispersed, and slurry-prepared to obtain a slurry.

[0008] Step (2): Add flotation agent to the slurry for flotation to separate zinc and iron in the slurry, and obtain iron-poor zinc-rich slurry and iron-rich zinc-poor slurry;

[0009] Step (3): Add the iron-rich and zinc-poor material slurry to a vertical mill or ball mill for scrubbing and grinding treatment, and then filter to obtain the ground solids;

[0010] Step (4): The grinding solids are successively subjected to preliminary crushing, drying, sieving and air jet pulverization and then conveyed to a hydrocyclone or air jet classifier for particle size classification to obtain zinc-rich material and iron-rich zinc-poor material; wherein the particle size of the zinc-rich material is smaller than that of the iron-rich zinc-poor material.

[0011] In step (4) of this invention, sieving is used to remove fragments with a diameter > 2 mm.

[0012] Typically, the zinc content of zinc-containing blast furnace dust ranges from 0.1 wt% to 25 wt%. The method described in this application requires a zinc content of ≥0.5 wt% in the raw materials. Due to environmental regulations, except for blast furnace dust transported by tanker trucks, the ash discharge process for other transport methods generally involves water spraying to prevent dust generation. Since the temperature of the blast furnace dust during discharge is typically around 200°C and it contains soluble salts, the ash tends to clump after water spraying. Clumping alters the overall particle size distribution. Therefore, a crushing method is used to restore the original particle size distribution as little as possible without altering it before water spraying, facilitating subsequent steps. In this invention, the crushing and slurry preparation step utilizes a ball mill or vertical mill, with grinding balls made of steel, zirconium oxide, or silicon dioxide. In this invention, the solid content of the slurry after crushing and preparation is 16 wt% to 30 wt%.

[0013] According to the method for removing zinc from zinc-containing blast furnace dust according to the present invention, preferably, in step (1), the mass ratio of zinc-containing blast furnace dust to water is 1:2-5.

[0014] According to the method for removing zinc from zinc-containing blast furnace dust according to the present invention, preferably, in step (1), when a ball mill is used in the crushing and slurry preparation step, the mass ratio of grinding balls to dry zinc-containing blast furnace dust is 6-12:1.

[0015] According to the method for removing zinc from zinc-containing blast furnace dust according to the present invention, preferably, in step (1), grinding balls with a diameter of 20 mm account for 5%-15% of the total mass of grinding balls, grinding balls with a diameter of 15 mm account for 25%-35% of the total mass of grinding balls, grinding balls with a diameter of 10 mm account for 25%-35% of the total mass of grinding balls, and grinding balls with a diameter of 5 mm account for 25%-35% of the total mass of grinding balls.

[0016] According to the method for removing zinc from zinc-containing blast furnace dust according to the present invention, preferably, in step (1), the ball milling time is 5-10 min and the motor frequency is 10-30 Hz.

[0017] According to the method for removing zinc from zinc-containing blast furnace dust according to the present invention, preferably, in step (1), the solid content of the slurry obtained by the crushing, dispersing and slurry preparation step is 16wt%-30wt%.

[0018] According to the present invention, in a method for removing zinc from zinc-containing blast furnace dust, preferably, in step (2), the flotation agent is sodium alkylbenzene sulfonate, the ratio of sodium alkylbenzene sulfonate to dry zinc-containing blast furnace dust is 2-10 g / kg, and the addition rate is 0.5-1.5 g / min.

[0019] In step (2) of this invention, when adding flotation agent to the slurry, it is necessary to add material, stir, and aerate simultaneously to enhance the foaming effect. At the same time, the generated foam is scraped off using a flotation machine until almost no foam is produced. The foam obtained is a lean iron and rich zinc slurry, and the remaining tailings are a rich iron and lean zinc slurry. The zinc-rich material obtained by filtering the lean iron and rich zinc slurry can be recycled as a zinc-containing raw material. The filtrate is returned to the ball mill crushing, dispersing, and slurry preparation step for reuse. The rich iron and lean zinc slurry then enters the next step of scrubbing and grinding to dissociate the zinc-containing minerals attached to the surface of large particles. The dissociated zinc-containing minerals have small particle sizes, which are easy to remove during subsequent air classification.

[0020] According to the present invention, a method for removing zinc from zinc-containing blast furnace dust, preferably, in step (3), before the scrubbing and grinding treatment, water is added to adjust the solid content of the iron-rich and zinc-poor slurry to 30wt%-55wt%.

[0021] According to the method for removing zinc from zinc-containing blast furnace dust according to the present invention, preferably, in step (3), after scrubbing and grinding treatment, the ore is filtered and the moisture content of the ground solid after filtration is 10%-20%.

[0022] In step (3) of the present invention, the equipment used for scrubbing and grinding is a vertical mill or a ball mill; preferably, the grinding ball material can be one of steel balls, zirconium oxide or silicon oxide; more preferably, the mass ratio of grinding balls to iron-rich and zinc-poor dry material is 6 to 12:1.

[0023] As a specific embodiment of the present invention, the grinding balls with a diameter of 15mm account for 10%-20% of the total mass of the grinding balls, the grinding balls with a diameter of 10mm account for 20%-25% of the total mass of the grinding balls, the grinding balls with a diameter of 5mm account for 25%-30% of the total mass of the grinding balls, and the grinding balls with a diameter of 2mm account for 30%-40% of the total mass of the grinding balls; preferably, the ball milling or vertical milling time is 2-7 minutes, and the motor frequency is 10-15Hz.

[0024] According to the present invention, a method for removing zinc from zinc-containing blast furnace dust, preferably, in step (4), the grading particle size is 20 μm, solids with a particle size less than 20 μm are zinc-rich materials, and solids with a particle size not less than 20 μm are iron-rich and zinc-poor materials.

[0025] According to the method for removing zinc from zinc-containing blast furnace dust according to the present invention, preferably, in step (4), the air classifying equipment is a hydrocyclone and an air classifier.

[0026] According to the present invention, in a method for removing zinc from zinc-containing blast furnace dust, preferably, in step (4), when the airflow classification device is a hydrocyclone, the diameter of the hydrocyclone barrel is not less than 50 mm, the feed pressure is 0.1-0.4 MPa, and the diameter of the hydrocyclone underflow outlet is not less than 16 mm.

[0027] According to the method for removing zinc from zinc-containing blast furnace dust according to the present invention, preferably, in step (4), when the air classifier is an air classifier, the frequency of the air classifier host is 30-65Hz, the frequency of the fan is 40-60Hz, and the air volume is 25-45m³. 3 / min. In one specific embodiment of the invention, after scrubbing and grinding, the ground solids obtained through filtration are initially crushed, dried, and sieved. The undersize material is sent to an air jet mill for pulverization and classification, while the oversize material is returned to the crushing process. The sieve mesh has an aperture of 2mm to ensure that the particle diameter is ≤2mm. The undersize material is conveyed by a belt to an air jet mill for further pulverization and dispersion. The purpose of air jet pulverization and dispersion is to dry the filtered, agglomerated, and initially crushed iron-rich and zinc-poor material and restore its original particle size distribution.

[0028] Through numerous experiments, the inventors discovered that zinc-containing minerals in the ground solids after grinding are mainly found in particles with a diameter ≤20μm, but some zinc-containing minerals still adhere to the surface of larger particles. The purpose of scrubbing grinding is to dissociate the zinc-containing minerals adhering to the surface of larger particles. The dissociated zinc-containing minerals have a smaller particle size, which facilitates further zinc removal in subsequent secondary cyclone processes. Iron-containing minerals are mainly found in particles with a diameter ≥50μm. In order to further remove zinc-containing minerals while minimizing iron loss, a classification particle size of 20μm was selected to separate particles <20μm and ≥20μm, obtaining zinc-rich slurry and iron-rich, zinc-poor slurry respectively. The filtrates obtained from both are returned to the ball milling and slurry preparation process for reuse. The obtained zinc-rich material can be recycled as a zinc extraction raw material, and the obtained iron-rich, zinc-poor material can be recycled as an ironmaking raw material.

[0029] The beneficial effects of this invention are:

[0030] This invention discloses a method for removing zinc from zinc-containing blast furnace dust. The zinc-containing blast furnace dust is crushed, dispersed, and slurried. Zinc- and iron-containing minerals in the slurry are separated by flotation. The obtained iron-rich and zinc-poor material is then scrubbed and ground to remove zinc-containing minerals from the surface of coarse particles. After filtration, it is coarsely crushed and then subjected to air jet milling and classification for deep zinc removal, resulting in iron-rich and zinc-poor material with very low zinc content. This method has a good zinc enrichment effect, and the zinc-rich and zinc-poor material after zinc removal can be used as raw material for blast furnace ironmaking. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples.

[0032] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0033] Example 1

[0034] Example 1 describes a method for removing zinc from zinc-containing blast furnace dust, comprising the following steps:

[0035] Step (1): After mixing zinc-containing blast furnace dust with a zinc content of 3wt% with water, the mixture is crushed, dispersed and slurry-prepared to obtain a slurry. The mass ratio of zinc-containing blast furnace dust to water is 1:4. When a ball mill is used for the crushing step, the mass ratio of steel grinding balls to dry zinc-containing blast furnace dust is 10:1. Grinding balls with a diameter of 20mm account for 15% of the total mass of grinding balls, grinding balls with a diameter of 15mm account for 25% of the total mass of grinding balls, grinding balls with a diameter of 10mm account for 30% of the total mass of grinding balls, and grinding balls with a diameter of 5mm account for 30% of the total mass of grinding balls. The ball milling time is 10min, the motor frequency is 30Hz, and the solid content of the slurry after preparation is 25wt%.

[0036] Step (2): The flotation agent is sodium alkylbenzene sulfonate. The ratio of sodium alkylbenzene sulfonate to zinc-containing blast furnace dust dry material is 2-10 g / kg, and the addition rate is 0.5-1.5 g / min.

[0037] In step (2) of this invention, a flotation agent is added to the slurry, and the agent is added while stirring and aerating to enhance the foaming effect. At the same time, the foam generated is scraped off by the flotation machine until the foam is basically no longer generated. The foam obtained is a lean iron and rich zinc slurry, and the remaining tailings are rich iron and lean zinc slurry. The flotation agent is sodium alkylbenzene sulfonate, and the ratio of sodium alkylbenzene sulfonate to zinc-containing blast furnace dust dry material is 8g / kg, and the addition rate is 1g / min. The zinc-rich material obtained by filtering the lean iron and rich zinc slurry can be recycled as a zinc-containing raw material. The filtrate is returned to the ball mill crushing and slurry preparation step for reuse, and the rich iron and lean zinc slurry enters the next step of scrubbing, grinding and decarburization.

[0038] Step (3): Add water to adjust the solid content of the iron-rich and zinc-poor material slurry to 40wt%. Add the iron-rich and zinc-poor material slurry to the vertical mill for scrubbing and grinding treatment, and then filter to obtain grinding solids. The water content in the grinding solids is 20wt%, and the grinding slurry is obtained. The equipment used for scrubbing and grinding treatment is a vertical mill. The mass ratio of steel grinding balls to dry iron-rich and zinc-poor material is 8:1. The mass of grinding balls with a diameter of 15mm accounts for 10% of the total mass of grinding balls, grinding balls with a diameter of 10mm account for 25% of the total mass of grinding balls, grinding balls with a diameter of 5mm account for 25% of the total mass of grinding balls, and grinding balls with a diameter of 2mm account for 40% of the total mass of grinding balls. The ball milling time is 5min, and the motor frequency is 10-15Hz.

[0039] Step (4): The grinding solids are initially crushed to a particle diameter of ≤2mm, dried, and then conveyed by belt to an air jet mill for air jet milling. After air jet milling, the solids are conveyed to a hydrocyclone for particle size classification to obtain zinc-rich material and iron-rich zinc-poor material. The particle size classification of the hydrocyclone is 20μm. Particles with a diameter less than 20μm are zinc-rich material, and particles with a diameter not less than 20μm are iron-rich zinc-poor material. The diameter of the hydrocyclone barrel is 100mm, the feed pressure is 0.3MPa, and the diameter of the hydrocyclone underpass nozzle is 20mm.

[0040] The zinc content of the iron-rich raw material obtained in Example 1 was found to be 0.19 wt%.

[0041] Example 2

[0042] Example 2 describes a method for removing zinc from zinc-containing blast furnace dust, comprising the following steps:

[0043] Step (1): After mixing zinc-containing blast furnace dust with a zinc content of 8wt% with water, the mixture is crushed, dispersed and slurry-prepared to obtain a slurry. The mass ratio of zinc-containing blast furnace dust to water is 1:4. When a ball mill is used for the crushing step, the mass ratio of steel grinding balls to dry zinc-containing blast furnace dust is 10:1. Grinding balls with a diameter of 20mm account for 15% of the total mass of grinding balls, grinding balls with a diameter of 15mm account for 25% of the total mass of grinding balls, grinding balls with a diameter of 10mm account for 30% of the total mass of grinding balls, and grinding balls with a diameter of 5mm account for 30% of the total mass of grinding balls. The ball milling time is 10min, the motor frequency is 30Hz, and the solid content of the slurry after preparation is 25wt%.

[0044] Step (2): The flotation agent is sodium alkylbenzene sulfonate. The ratio of sodium alkylbenzene sulfonate to zinc-containing blast furnace dust dry material is 2-10 g / kg, and the addition rate is 0.5-1.5 g / min.

[0045] In step (2) of this invention, a flotation agent is added to the slurry, and the agent is added while stirring and aerating to enhance the foaming effect. At the same time, the foam generated is scraped off by the flotation machine until the foam is basically no longer generated. The foam obtained is a lean iron and rich zinc slurry, and the remaining tailings are rich iron and lean zinc slurry. The flotation agent is sodium alkylbenzene sulfonate, and the ratio of sodium alkylbenzene sulfonate to zinc-containing blast furnace dust dry material is 8g / kg, and the addition rate is 1g / min. The zinc-rich material obtained by filtering the lean iron and rich zinc slurry can be recycled as a zinc-containing raw material. The filtrate is returned to the ball mill crushing and slurry preparation step for reuse, and the rich iron and lean zinc slurry enters the next step of scrubbing, grinding and decarburization.

[0046] Step (3): Add water to adjust the solid content of the iron-rich and zinc-poor material slurry to 40wt%. Add the iron-rich and zinc-poor material slurry to the vertical mill for scrubbing and grinding treatment, and then filter to obtain grinding solids. The water content of the grinding solids is 20wt%, and the grinding slurry is obtained. The equipment used for scrubbing and grinding treatment is a vertical mill. The mass ratio of steel grinding balls to dry iron-rich and zinc-poor material is 8:1. The mass of grinding balls with a diameter of 15mm accounts for 10% of the total mass of grinding balls, grinding balls with a diameter of 10mm account for 25% of the total mass of grinding balls, grinding balls with a diameter of 5mm account for 25% of the total mass of grinding balls, and grinding balls with a diameter of 2mm account for 40% of the total mass of grinding balls. The vertical milling time is 5min, and the motor frequency is 10-15Hz.

[0047] Step (4): The ore-ground solids are initially crushed, dried, and sieved through a 2mm sieve. The material oversizes is returned for further coarse crushing, and the material undersizes is dried and then subjected to air jet agitation to obtain pulverized material. The air jet agitation equipment is an air jet mill with an air flow rate of 0.6 m³ / h. 3 The airflow pulverizer operates at a speed of 100 m³ / min and an air pressure of 2 MPa. After pulverization, the material is conveyed to an airflow classifier for particle size classification, yielding zinc-rich and iron-rich, zinc-poor materials. The airflow classifier has a particle size limit of 20 μm; particles smaller than 20 μm are classified as zinc-rich, and particles with a size not smaller than 20 μm are classified as iron-rich, zinc-poor. The airflow classifier operates at a frequency of 50 Hz, the fan frequency is 50 Hz, and the airflow volume is 33 m³ / min. 3 / min.

[0048] The zinc content of the iron-rich raw material obtained in Example 2 was found to be 0.21 wt%.

[0049] Comparative Example 1

[0050] Comparative Example 1: Zinc-containing blast furnace dust with a zinc content of 10 wt% was used to prepare lean zinc feed according to the method in Example 1 of Chinese Patent CN110743714B. The zinc content of the resulting lean zinc feed was about 2.4 wt%. For blast furnace ironmaking, the zinc content is too high and cannot be used as raw material for blast furnace ironmaking, which is not conducive to the stable and smooth operation of the blast furnace.

[0051] It should be noted that the components or steps in the above embodiments can be interchanged, substituted, added, or deleted. Therefore, the combinations formed by these reasonable permutations and transformations should also fall within the protection scope of this invention, and the protection scope of this invention should not be limited to the above embodiments.

[0052] The above are exemplary embodiments disclosed in this invention. The order of the disclosed embodiments is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. However, it should be noted that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of this invention (including the claims) is limited to these examples. Various changes and modifications can be made without departing from the scope defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular.

[0053] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for removing zinc from zinc-containing blast furnace dust, characterized in that, Includes the following steps: Step (1): After mixing zinc-containing blast furnace dust and water, the mixture is crushed, dispersed, and slurry-prepared to obtain a slurry. Step (2): Add flotation agent to the slurry for flotation to separate zinc and iron in the slurry, and obtain iron-poor zinc-rich slurry and iron-rich zinc-poor slurry; Step (3): Add the iron-rich and zinc-poor material slurry to a vertical mill or ball mill for scrubbing and grinding treatment, and then filter to obtain grinding solids; before scrubbing and grinding treatment, add water to adjust the solid content of the iron-rich and zinc-poor material slurry to 30wt%-55wt%, and after scrubbing and grinding treatment, filter to obtain grinding solids with a moisture content of 10%-20%; the equipment used for scrubbing and grinding treatment is a vertical mill or ball mill, and the mass ratio of grinding balls to dry iron-rich and zinc-poor material is 6~12:1; Step (4): The grinding solids are successively subjected to preliminary crushing, drying, sieving and air jet milling and then conveyed to a hydrocyclone or air classifier for particle size classification to obtain zinc-rich material and iron-rich zinc-poor material; the sieve mesh size is 2mm; the classification particle size is 20µm, solids with a particle size less than 20µm are zinc-rich material, and solids with a particle size not less than 20µm are iron-rich zinc-poor material; In step (1), the crushing, dispersing and slurry preparation step uses a ball mill or a vertical mill, and the mass ratio of grinding balls to zinc-containing blast furnace dust dry material is 6-12:1; In step (1), grinding balls with a diameter of 20mm account for 5%-15% of the total mass of the grinding balls, grinding balls with a diameter of 15mm account for 25%-35% of the total mass of the grinding balls, grinding balls with a diameter of 10mm account for 25%-35% of the total mass of the grinding balls, and grinding balls with a diameter of 5mm account for 25%-35% of the total mass of the grinding balls. In step (1), the solid content of the slurry obtained from the crushing, dispersing, and slurry preparation step is 16wt%-30wt%; In step (2), the flotation agent is sodium alkylbenzene sulfonate, and the ratio of sodium alkylbenzene sulfonate to zinc-containing blast furnace dust dry material is 2-10 g / kg, with an addition rate of 0.5-1.5 g / min.

2. The method for removing zinc from zinc-containing blast furnace dust according to claim 1, characterized in that, In step (1), the mass ratio of zinc-containing blast furnace dust to water is 1:2-5.

3. The method for removing zinc from zinc-containing blast furnace dust according to claim 1, characterized in that, In step (1), the ball milling time is 5-10 min and the motor frequency is 10-30 Hz.