Method for producing alkaline pellets by dezincification of zinc-containing dust

Abstract

The invention discloses a method for producing alkaline pellets by dezincification of zinc-containing dust, which is characterized by comprising the following steps of: (1) fully and uniformly mixing the zinc-containing dust and a calcification agent in proportion, and then adding a binder and water to carry out pelletizing treatment to obtain zinc-containing dust green pellets; and after the obtained zinc-containing dust green pellets are dried, preheated and roasted, ammonia leaching treatment is adopted, zinc is recycled from obtained zinc-containing leaching liquid through an electrolytic method, and the leached pellets are dried. And (2) carrying out secondary roasting treatment on the pellets leached in the step (1) to obtain alkaline pellets. By means of the method, the zinc-containing dust of the steel plant can be absorbed in the plant, meanwhile, efficient production of the alkaline pellets is achieved, and the method plays an important role in promoting the purposes of energy conservation and consumption reduction in steel production.

Description

Technical Field

[0001] The invention belongs to the field of iron and steel metallurgy and ore dressing and separation, and relates to a method for producing alkaline pellets by dezincifying zinc-containing dust. Background Art

[0002] As the cornerstone of my country's economic development, the steel industry not only occupies an important position in the national economy, but is also one of the main sources of solid waste emissions. In the steel production process, especially in the smelting process, a large amount of dust will be generated, of which zinc-containing dust accounts for about 8%-12% of the total steel production, and zinc-containing dust itself contains about 20%-30% zinc, which makes it a valuable secondary resource, rich in iron, zinc and other valuable metal elements. At present, the traditional methods for treating zinc-containing dust in the steel industry mainly include pyrometallurgy, hydrometallurgy and pyrometallurgy-wet combined methods. Although wet treatment has certain advantages in environmental protection, its zinc leaching rate and production efficiency are relatively low, and the leaching slag produced is difficult to recycle and difficult to meet the stacking requirements of environmental protection regulations. In contrast, the pyrometallurgical process has obvious advantages in processing efficiency and scale, but it cannot achieve the extraction of non-ferrous metal elements. The fire-wet combined method combines the advantages of both. Through fire pretreatment, zinc oxide and sponge iron rich in multiple elements are obtained, and then valuable elements are further extracted through wet methods. This has become a new trend in the development of zinc dust resource utilization technology in steel plants. With increasingly stringent environmental protection standards, steel companies are faced with the challenge of how to internally dispose of zinc dust and achieve its efficient recycling.

[0003] In addition, my country's blast furnace ironmaking mainly adopts a charge structure of high-basicity sintered ore with acidic pellets and a small amount of lump ore. Although this structure can improve economic benefits, it has major problems in terms of pollution and energy consumption. The pollution load of the sintering process is 5 times that of the pelletizing process, the sulfur dioxide emission is 2 times that of the pelletizing process, and the energy consumption is also 2 times that of the pelletizing process. The use of pellets can significantly improve the grade and reduce the fuel ratio, which is in line with the current policy and industry development trend, and promote the transformation of blast furnace ironmaking to green development. Practice has proved that increasing the proportion of pellets into the furnace can effectively reduce the slag volume and fuel consumption, while improving the blast furnace utilization coefficient. However, simply increasing the proportion of ordinary acidic pellets cannot meet the slag making system requirements in the blast furnace ironmaking process. In order to stabilize the blast furnace slag type and increase the basicity of the pellets, it is necessary to replace the high-basicity sintered ore with alkaline pellets to build a new charge structure dominated by pellets. The development of high-proportion pellet smelting technology, especially the preparation technology of alkaline pellets, has become an important research direction in the steel industry.

[0004] The preparation process of alkaline pellets usually involves adding limestone powder in proportion during the production process, mixing it with raw materials such as iron ore powder and bentonite to form green balls, which are then preheated and roasted to form finished products. However, the use of limestone powder as a flux requires it to be ground to an extremely fine particle size, and the heat absorption of limestone decomposition during the roasting process of alkaline pellets will lead to high production energy consumption and lower production efficiency than acidic pellets. At the same time, the added limestone will also reduce the grade of the pellets. In the face of the continuous improvement of energy conservation and environmental protection requirements in the steel industry, how to efficiently utilize the large amount of zinc-containing dust generated by steel mills and how to achieve efficient production of alkaline pellets have become key issues that steel companies urgently need to solve. The development of a new technology that can simultaneously achieve efficient utilization of zinc-containing dust and efficient preparation of alkaline pellets is of great significance to promoting the sustainable development of the steel industry. Summary of the invention

[0005] In view of a series of difficulties encountered by steel enterprises in dealing with zinc-containing dust, the purpose of the present invention is to provide a method for dezincifying zinc-containing dust to produce alkaline pellets, which can achieve efficient recycling of zinc-containing dust and production of alkaline pellets, and is conducive to achieving energy conservation and consumption reduction and reducing carbon emissions in steel plants.

[0006] The present invention provides the following technical solutions:

[0007] A method for producing alkaline pellets by dezincifying zinc-containing dust comprises the following steps:

[0008] (1) fully mixing zinc-containing dust and a calcifying agent in proportion, adding a binder and water to perform a ball-forming treatment to obtain zinc-containing dust green balls; drying, preheating, calcifying and roasting the obtained zinc-containing dust green balls, and then leaching them with ammonia, filtering them to obtain a filtrate and leached pellets, and drying the leached pellets;

[0009] In the zinc-containing dust raw ball, the molar ratio is CaO / (ZnO+Fe 2 O 3 ) = 2.0-3.0, preferably 2.0-2.1;

[0010] The preheating temperature is 700-1050°C, preferably 700-750°C, the preheating time is 5-20min, the calcination temperature is 1100-1300°C, preferably 1250-1300°C, and the calcination time is 0.5-3 hours;

[0011] (2) The pellets leached in step (1) are subjected to secondary roasting treatment to obtain alkaline pellets; the secondary roasting temperature is 1000-1200° C. and the roasting time is 10-30 min.

[0012] In a preferred embodiment, the calcifying agent in step (1) is selected from at least one of calcium-containing substances such as calcium carbonate, calcium oxide, calcium hydroxide, limestone, and slaked lime, and the particle size of the calcium-containing substance is controlled at -200 mesh ≥ 80%.

[0013] In a preferred embodiment, the binder in step (1) includes one or more of bentonite, organic binder, composite binder, etc. In industrial applications, the binder is selected from at least one of bentonite and sodium carboxymethyl starch.

[0014] When used in industry, 8-10% of water and 0.5-2.5%, preferably 1-2% of a binder are added to the raw ore to make green balls in step (1). The raw ore is the zinc-containing dust and the calcifying agent.

[0015] The calcifying agent is preferably slaked lime.

[0016] In a preferred embodiment, the pellet size range of step (1) is 8-20 mm.

[0017] In a preferred embodiment, the drying temperature in step (1) is 200-400° C., and the drying time is 2-10 min.

[0018] In the present invention, the zinc dust raw ball is controlled, and the CaO and (ZnO+Fe 2 O 3 ) is 2.0-3.0 and the strategy of first pelletizing and then preheating + roasting is adopted, which can not only achieve efficient Zn leaching, but also provide the necessary conditions for obtaining high-strength alkaline pellets in the subsequent process. More importantly, due to the use of the strategy of pelletizing + preheating + roasting with appropriate parameters in the early stage, it is not necessary to make pellets again in the later stage, and it can be directly used for blast furnace smelting after roasting at 1000-1200℃.

[0019] In a preferred embodiment, the filtrate obtained in step (1) can be electrolytically used to recover zinc.

[0020] In a preferred embodiment, the ammonia immersion solution in step (1) is NH 3 ·H 2 O and NH 4 Cl or ammonium sulfate.

[0021] In a preferred embodiment, during the ammonia leaching in step (1), the solid-liquid ratio is 95-105 g / L, the leaching temperature is 40-70° C., the leaching time is 90-150 min, and the NH 4 Cl or ammonium sulfate and NH 3 ·H 2 The molar concentration ratio of O is 0.8-1.2:0.8-1.2, and the total ammonia concentration in the leachate is 4-8 mol / L.

[0022] The secondary calcination temperature is lower than the calcination temperature in step (1).

[0023] The compressive strength of the alkaline pellets obtained by secondary roasting in the present invention is greater than 2500N / P, and fully meets the requirements of blast furnace smelting.

[0024] When applied in industry, after leaching, the present invention can obtain alkaline pellets with a compressive strength greater than 2500N / P when secondary roasting is performed even at 1000-1100°C.

[0025] The present invention aims to convert zinc ferrite in zinc-containing dust into an easily extractable zinc oxide form through a step-by-step calcination roasting process, which is convenient for the subsequent ammonia leaching process. This conversion not only reduces the leaching cost, but also improves the selectivity, ensuring that other impurities are not leached. The calcifying agent used is not only inexpensive and easy to obtain, but also has a fast reaction speed, and the leaching rate of zinc can exceed 90%. The pellets after leaching can be prepared into alkaline pellet furnace charge that meets the needs of blast furnace smelting through secondary roasting. The secondary roasting temperature is low, and a furnace charge that meets the requirements of the blast furnace can be obtained. The present invention not only promotes the effective consumption of zinc-containing dust inside the steel plant, but also promotes the efficient production of alkaline pellets. The overall process is short, which helps to realize the recycling of zinc-containing dust in the steel plant. Under the background of the dual carbon goals, it has a significant driving effect on achieving the energy-saving and consumption-reducing goals of the steel industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart of Example 1 of the present invention. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are further described below by way of examples, but the specific embodiments of the present invention are not limited to the following examples.

[0028] In the embodiments of the present invention, unless otherwise specified, the means used are all conventional means in the art, and the reagents used can be obtained through conventional commercial channels.

[0029] The technical solution of the present invention is described in detail below through specific embodiments and drawings.

[0030] Example 1

[0031] A zinc-containing dust (TZn 10.12%, ZnFe 2 O 4 67.12%), add slaked lime to control CaO / (ZnO+Fe 2 O 3) is 2.0:1, and 10% of the original ore mass of water and 2% of the original ore mass of bentonite (the original ore is the zinc-containing dust and slaked lime) are added at the same time. After being fully mixed, the raw balls are granulated into 8-20 mm green balls, and the green balls are dried, preheated and roasted. The drying temperature is 200°C, the drying time is 10 min, the preheating temperature is 700°C, the preheating time is 20 min, the roasting temperature is 1300°C, the roasting time is 0.5 hour, and the ammonia leaching treatment is carried out after cooling. The ammonia leaching system is: the solid-liquid ratio is 100 g / L, the leaching temperature is 60°C, the leaching time is 120 min, and the leaching liquid is NH 4 Cl-NH 3 ·H 2 O solution (NH 4 Cl and NH 3 ·H 2 The molar concentration ratio of O is 1:1), the total ammonia concentration in the leachate is 6 mol / L, and the zinc leaching rate is 92.11% after the leachate is filtered. The zinc is subsequently recovered by electrolysis. After leaching, the pellets are dried and then subjected to secondary roasting treatment at a temperature of 1200°C for 10 minutes to obtain alkaline pellets with a compressive strength of 2789N / P.

[0032] Example 2

[0033] A zinc-containing dust (TZn 10.12%, ZnFe 2 O 4 67.12%), add limestone to control CaO / (ZnO+Fe 2 O 3 ) is 2.5:1, 9% of the original ore mass of water and 1% of the original ore mass of bentonite (the original ore is the zinc-containing dust and quicklime used), and the raw balls are fully mixed and granulated into 8-20 mm green balls, and the green balls are dried, preheated and roasted. The drying temperature is 300°C, the drying time is 6 minutes, the preheating temperature is 800°C, the preheating time is 15 minutes, the roasting temperature is 1250°C, the roasting time is 1 hour, and the ammonia leaching treatment is carried out after cooling. The ammonia leaching system is: the solid-liquid ratio is 100g / L, the leaching temperature is 40°C, the leaching time is 180 minutes, and the leaching liquid is ammonium sulfate-NH 3 ·H 2 O solution (ammonium sulfate and NH 3 ·H 2 The molar concentration ratio of O is 1:1), the total ammonia concentration in the leachate is 6 mol / L, and the zinc leaching rate is 93.15% after the leachate is filtered. The zinc is subsequently recovered by electrolysis. After leaching, the pellets are dried and then subjected to secondary roasting treatment at a temperature of 1100°C for 20 minutes to obtain alkaline pellets with a compressive strength of 2675N / P.

[0034] Example 3

[0035] A zinc-containing dust (TZn 10.12%, ZnFe 2 O 4 67.12%), add calcium oxide to control CaO / (ZnO+Fe 2 O 3 ) is 3.0:1, and 8% of water by mass of the original ore, 0.5% of bentonite by mass of the original ore and 0.2% of sodium carboxymethyl starch CMS (the original ore is the zinc dust and quicklime used) are added at the same time, and the mixture is fully mixed and granulated into small balls of 8-20 mm, and the raw balls are dried, preheated and roasted, with a drying temperature of 400°C and a drying time of 4 min, a preheating temperature of 900°C and a preheating time of 10 min, a roasting temperature of 1200°C and a roasting time of 1.5 hours, and then cooled and subjected to ammonia leaching treatment, and the ammonia leaching system is as follows: solid-liquid ratio of 100 g / L, leaching temperature of 40°C, leaching time of 180 min, and leaching liquid of NH 4 Cl-NH 3 ·H 2 O solution (NH 4 Cl and NH 3 ·H 2 The molar concentration ratio of O is 1:1), the total ammonia concentration in the leachate is 6 mol / L, and the zinc leaching rate is 93.43% after the leachate is filtered. The zinc is subsequently recovered by electrolysis. After leaching, the pellets are dried and then subjected to secondary roasting treatment at a temperature of 1000°C for 30 minutes to obtain alkaline pellets with a compressive strength of 2594N / P.

[0036] Comparative Example 1

[0037] A zinc-containing dust (TZn 10.12%, ZnFe 2 O 4 67.12%), add quicklime to control CaO / (ZnO+Fe 2 O 3 ) in a molar ratio of 2.0:1, and then heated to 1300°C after being fully mixed, roasted for 0.5 hours, and then cooled for ammonia leaching. The ammonia leaching system is: solid-liquid ratio of 100g / L, leaching temperature of 60°C, leaching time of 120min, and leaching liquid of NH 4 Cl-NH 3 ·H 2 O solution (NH 4 Cl and NH 3 ·H 2O molar concentration ratio is 1:1), the total ammonia concentration in the leachate is 6 mol / L, and the zinc leaching rate is 85.23% after the leachate is filtered (the filtering speed is slow during filtering). After leaching, the leached residue solid is finely ground to -200 mesh>80% after drying, and 9% water and 2.0% bentonite of the leached residue are added. After fully mixing, the pellets are granulated into 8-20 mm small balls; the small balls are dried and then calcined for a second time, the drying temperature is 400°C, the drying time is 4min, the secondary calcination temperature is 1200°C, and the time is 10min, to obtain alkaline pellets with a compressive strength of 2256N / P.

[0038] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. For those skilled in the art, improvements and changes obtained without departing from the technical concept of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for producing alkaline pellets by dezincifying zinc-containing dust, characterized in that: The following steps are involved: (1) fully mixing zinc-containing dust and a calcifying agent in proportion, adding a binder and water to perform a ball-forming treatment to obtain zinc-containing dust green balls; drying, preheating, calcifying and roasting the obtained zinc-containing dust green balls, and then leaching them with ammonia, filtering them to obtain a filtrate and leached pellets, and drying the leached pellets; In the zinc-containing dust green ball, the molar ratio is CaO / (ZnO+Fe2O3)=2.0-3.0; The preheating temperature is 700-1050°C, the preheating time is 5-20 minutes, the calcination temperature is 1100-1300°C, and the calcination time is 0.5-3 hours; (2) The pellets leached in step (1) are subjected to secondary roasting treatment to obtain alkaline pellets; the secondary roasting temperature is 1000-1200° C., and the roasting time is 10-30 minutes.

2. The method for producing alkaline pellets by dezincifying zinc-containing dust according to claim 1, characterized in that: The calcifying agent in step (1) is selected from at least one of calcium-containing substances such as calcium carbonate, calcium oxide, calcium hydroxide, limestone, slaked lime, etc., and the particle size of the calcium-containing substance is controlled at -200 mesh ≥ 80%.

3. The method for producing alkaline pellets by dezincifying zinc-containing dust according to claim 1, characterized in that: In step (1), the binder includes one or more of bentonite, organic binder, composite binder, etc.

4. The method for producing alkaline pellets by dezincifying zinc-containing dust according to claim 1, characterized in that: In step (1), 8-10% of water and 0.5-2.5%, preferably 1-2% of a binder are added to form green balls. The raw ore is the zinc-containing dust and the calcifying agent.

5. The method for producing alkaline pellets by dezincifying zinc-containing dust according to claim 1, characterized in that: The pellet size range of step (1) is 8-20 mm.

6. The method for producing alkaline pellets by dezincifying zinc-containing dust according to claim 1, characterized in that: The drying temperature in step (1) is 200-400° C., and the drying time is 2-10 min.

7. The method for producing alkaline pellets by dezincifying zinc-containing dust according to claim 1, characterized in that: The filtrate obtained in step (1) can be used to recover zinc by electrolysis.

8. The method for producing alkaline pellets by dezincifying zinc-containing dust according to claim 1, characterized in that: The ammonia immersion solution in step (1) is composed of NH3·H2O and NH4Cl or ammonium sulfate.

9. The method for producing alkaline pellets by dezincifying zinc-containing dust according to claim 8, characterized in that: During the ammonia leaching in step (1), the solid-liquid ratio is 100 g / L, the leaching temperature is 40-70° C., the leaching time is 90-150 min, the molar concentration ratio of NH4Cl / ammonium sulfate and NH3·H2O in the leaching solution is 0.8-1.2:0.8-1.2, and the total ammonia concentration in the leaching solution is 4-8 mol / L.

10. The method for producing alkaline pellets by dezincifying zinc-containing dust according to claim 1, characterized in that: The compressive strength of the alkaline pellets obtained by secondary roasting is greater than or equal to 2500N / P.

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