A method for comprehensive utilization of zinc-containing dust in steel plants

Abstract

The invention belongs to the technical field of iron and steel metallurgy, and discloses a method for comprehensively utilizing zinc-containing dust in a steel plant, comprising the following steps: 1) preparing raw materials: five kinds of iron-containing dust, namely, converter dust mud, blast furnace raw material ash (stockyard ash), blast furnace dry process ash (bag dust), blast furnace gas ash (blast furnace gravity ash), and steelmaking secondary dust; the binder is gelatinized starch, bentonite, quicklime, and limonite is added; 2) mixing the ingredients into balls, mixing the ingredients according to the weight ratio of dry materials, and mixing the five kinds of steel plant dust, the binder and The ore blending scheme of limonite is: converter mud 20%-25%, blast furnace raw material ash 12%-15%, blast furnace dry ash 10%-12%, blast furnace gas ash 3%-7%, steelmaking secondary dust 2%-3%, limonite 40%-45%, gelatinized starch 0.8%-1.5%, bentonite 0.7%-1.0%, quicklime 1.0-1.4%; 3) high temperature roasting, at a roasting temperature of 1000℃-1100℃, and a time of 20-25min. The obtained metallized agglomerate has a compressive strength of ≥2250N / ball, a 2.0m drop strength of ≥6 times / ball, TFe ≥63.0%, a metallization rate of ≥92.58%, and a dezincification rate of ≥92.0%. The metal agglomerate meets the production requirements of blast furnaces.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for comprehensively utilizing zinc-containing dust in a steel plant. Background Art

[0002] A large amount of dust and sludge is generated during the steel production process. Since these dusts contain a large number of useful elements, they need to be recycled. If they are discarded at will, it will not only pollute the environment, but also waste resources. The traditional sintering process can recycle iron well, but the zinc, lead and other elements in the dust will affect the quality of the sintered ore and even affect the normal production of the blast furnace. In order to recover useful components and remove zinc, lead and other elements that are harmful to blast furnace production, many studies have adopted direct reduction roasting to produce metallized pellets for blast furnaces or electric furnaces, and collect zinc oxide in the flue gas, so as to achieve the purpose of no waste leaving the factory and comprehensive utilization of resources.

[0003] Many steel companies and research institutes have also conducted extensive research on the dust generated during the production of domestic steel mills, and most of them use agglomeration fire reduction roasting to recover iron and zinc. For example, the patent with application number CN202211160796 discloses a method for the coordinated disposal of fly ash and blast furnace bag dust ash. This method briquettes fly ash, blast furnace bag dust ash, iron ore powder, coal powder, and binder. The pre-reduced cold briquettes enter the electric furnace for melting, and finally obtain two products, molten iron and ultrafine ceramic fibers. It can effectively absorb the solid waste generated by blast furnaces and the power industry, but this process treats fly ash and blast furnace bag dust. For example, the patent with application number CN202211082027.0 discloses a process, system and method for iron and zinc extraction based on a rotary kiln. The method granulates zinc-containing dust in a steel plant and roasts it in a rotary kiln to recover metallic iron and zinc oxide. The particles produced are very small, ranging from 1 to 10 mm, and slag iron and zinc oxide are finally obtained. However, the process is relatively complex and difficult to control. The patent with application number CN202220928384.3 discloses a production line for treating iron and steel metallurgical dust based on the rotary hearth furnace method. The dust is pressed into balls and reduced in a rotary hearth furnace to obtain metallized pellets and zinc-containing dust. The binder composition of this method is relatively complex, and the metallization rate of the final metallized pellets is below 90%.

[0004] In order to make the metallized pellets meet the purpose of blast furnace production and produce zinc oxide, the collected iron-containing ash and dust need to be pre-blocked. Since the process of using these block-shaped iron-containing materials has certain requirements on the iron content, strength and impurity content of the blocks, it is necessary to reasonably design the batching and binder system of the blocks to meet the requirements of blast furnace production.

[0005] Many literatures have also studied some of the dust in steel plants, mostly focusing on a portion of the dust, and the strength of the final metallized agglomerates is relatively low. Summary of the invention

[0006] The object of the present invention is to provide a method for simultaneously using a variety of steel plant dusts in a reasonable combination, using the carbon contained in the dust itself to reduce and produce metallized agglomerates for blast furnace production, and recovering zinc oxide at the same time.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A method for comprehensively utilizing zinc-containing dust in a steel plant of the present invention is characterized by comprising the following steps:

[0009] Step 1: Raw material preparation

[0010] Dust includes five types of iron-containing dust, including converter dust, blast furnace raw material ash (stockyard ash), blast furnace dry process ash (bag dust), blast furnace gas ash (blast furnace gravity ash), and steelmaking secondary dust. Gelatinized starch, bentonite, quicklime, and limonite are also used. Grind the limonite finely to a specific surface area of ​​≥1200cm 2 / g. Measure the moisture content of each raw material;

[0011] Step 2: Make the ingredients into balls

[0012] The 5 kinds of steel mill dust prepared in step 1, as well as gelatinized starch, bentonite, quicklime and limonite are mixed according to the dry weight ratio. Converter mud 20% to 25%, blast furnace raw material ash 12% to 15%, blast furnace dry ash 10% to 12%, blast furnace gas ash 3% to 7%, steelmaking secondary dust 2% to 3%, limonite 40% to 45%, gelatinized starch 0.8% to 1.5%, bentonite 0.7% to 1.0%, quicklime 1.0 to 1.4%. Ensure that the iron grade of the raw pressed mass is ≥ 53.0%, and the C content of the raw pressed mass is 3.5% to 4.0%. The pressed mass is formed by the pressing process, and the outer dimensions of the pressed mass are: diameter 30mm, height 20mm. The external pressure during pressing is 90MPa to 100MPa.

[0013] Step 3: High temperature calcination

[0014] The pressed mass obtained in step 2 is dried and then calcined in a vertical tube furnace at a temperature of 1000°C to 1100°C for 10 to 25 minutes; nitrogen is introduced during the calcination process and the generated smoke is collected. The pressed mass is taken out after calcination and cooled in nitrogen to obtain a metallized mass.

[0015] In step 2, the raw pressed ball has the following strength parameters: drop strength ≥ 5.0 times / 0.5m, compressive strength ≥ 200N / ball.

[0016] In step three, the metallized agglomerate has a compressive strength of ≥2250N / ball, a 2.0m drop strength of ≥6 times / ball, a TFe of ≥63.0%, a metallization rate of ≥92.58%, and a dezincification rate of ≥92.0%.

[0017] Compared with the prior art, the advantages of the present invention are:

[0018] 1. The present invention uses a variety of dust types, covering almost all types of dust in steel plants;

[0019] 2. The binder and limonite used in combination with the dust in the present invention are relatively cheap and easy to obtain;

[0020] 3. The raw pressed dough of the present invention has high strength, which reduces the difficulty of production;

[0021] 4. The roasting temperature of the present invention is relatively low, saving energy consumption;

[0022] 5. The strength and composition of the final metallized agglomerate of the present invention meet the requirements for use in blast furnaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Refer to the following Figure 1 The present invention is further illustrated by the following embodiments.

[0024] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0025] The present invention is described in detail below by specific examples, but the protection scope of the present invention is not limited. Unless otherwise specified, the experimental methods used in the present invention are all conventional methods, and the experimental equipment, materials, reagents, etc. used can be obtained from commercial channels.

[0026] Example 1

[0027] Step 1: Raw material preparation

[0028] The main chemical components of the raw materials of Example 1 are shown in Table 1:

[0029] Table 1 Main chemical components of raw materials used in Example 1

[0030]

[0031] Grind the limonite finely to a specific surface area of ​​≥1200cm 2 / g. Measure the moisture content of each raw material;

[0032] Step 2: Make the ingredients into balls

[0033] Converter mud 22%, blast furnace raw material ash 15%, blast furnace dry process ash 10%, blast furnace gas ash 7%, steelmaking secondary dust 2%, limonite 42.0%, gelatinized starch 1.0%, bentonite 0.5%, quicklime 0.5%. Add 8.0% water, mix well and press into a ball; 0.5m drop strength 5.6 times / ball, compressive strength 220N / ball.

[0034] Step 3: High temperature calcination

[0035] The pressed agglomerate obtained in step 2 is dried and then roasted in a vertical tube furnace at a preheating temperature of 1000°C for 25 minutes; nitrogen is introduced during the roasting process and the generated smoke is collected. The pressed agglomerate is taken out after the roasting is completed and cooled in nitrogen to obtain a metallized agglomerate. The metallized agglomerate has a compressive strength of 2350N / ball, a 2.0m drop strength of 8 times / ball, a TFe of 63.6%, a metallization rate of 93.6%, and a dezincification rate of 92.3%.

[0036] Example 2

[0037] Step 1: Raw material preparation

[0038] The main chemical components of the raw materials of Example 2 are shown in Table 1:

[0039] Grind the limonite finely to a specific surface area of ​​≥1200cm 2 / g. Measure the moisture content of each raw material;

[0040] Step 2: Make the ingredients into balls

[0041] Converter mud 20%, blast furnace raw material ash 12%, blast furnace dry ash 12%, blast furnace gas ash 5%, steelmaking secondary dust 3%, limonite 45.0%, gelatinized starch 1.0%, bentonite 1.0%, quicklime 1.0%. Add 8.0% water, mix well and press into a ball; 0.5m drop strength 6.2 times / ball, compressive strength 264N / ball.

[0042] Step 3: High temperature calcination

[0043] The pressed agglomerate obtained in step 2 is dried and then roasted in a vertical tube furnace at a preheating temperature of 1000°C for 25 minutes; nitrogen is introduced during the roasting process and the generated smoke is collected. The pressed agglomerate is taken out after the roasting is completed and cooled in nitrogen to obtain a metallized agglomerate. The metallized agglomerate has a compressive strength of 2420N / ball, a 2.0m drop strength of 8 times / ball, a TFe of 64.2%, a metallization rate of 93.5%, and a dezincification rate of 92.1%.

[0044] Example 3

[0045] Step 1: Raw material preparation

[0046] The main chemical components of the raw materials of Example 3 are shown in Table 1:

[0047] Grind the limonite finely to a specific surface area of ​​≥1200cm 2 / g. Measure the moisture content of each raw material;

[0048] Step 2: Make the ingredients into balls

[0049] Converter mud 24%, blast furnace raw material ash 12%, blast furnace dry ash 12%, blast furnace gas ash 3%, steelmaking secondary dust 3%, limonite 44.0%, gelatinized starch 1.0%, bentonite 0.5%, quicklime 0.5%. Add 8.0% water, mix well and press into a ball; 0.5m drop strength 5.3 times / ball, compressive strength 221N / ball.

[0050] Step 3: High temperature calcination

[0051] The pressed mass obtained in step 2 is dried and then roasted in a vertical tube furnace at a preheating temperature of 1100°C for 20 minutes; nitrogen is introduced during the roasting process and the generated smoke is collected. The pressed mass is taken out after the roasting is completed and cooled in nitrogen to obtain a metallized mass. The metallized mass has a compressive strength of 2880N / ball, a 2.0m drop strength of 6 times / ball, a TFe of 63.9%, a metallization rate of 93.2%, and a dezincification rate of 92.2%.

[0052] Example 4

[0053] Step 1: Raw material preparation

[0054] The main chemical components of the raw materials of Example 4 are shown in Table 1:

[0055] Grind the limonite finely to a specific surface area of ​​≥1200cm 2 / g. Measure the moisture content of each raw material;

[0056] Step 2: Make the ingredients into balls

[0057] Converter mud 20%, blast furnace raw material ash 12%, blast furnace dry ash 12%, blast furnace gas ash 5%, steelmaking secondary dust 3%, limonite 45.0%, gelatinized starch 1.0%, bentonite 1.0%, quicklime 1.0%. Add 8.0% water, mix well and press into a ball; 0.5m drop strength 6.2 times / ball, compressive strength 264N / ball.

[0058] Step 3: High temperature calcination

[0059] The pressed agglomerates obtained in step 2 are dried and then roasted in a vertical tube furnace at a preheating temperature of 1100°C for 20 minutes; nitrogen is introduced during the roasting process and the generated smoke is collected. The pressed agglomerates are taken out after the roasting and cooled in nitrogen to obtain metallized agglomerates. The metallized agglomerates have a compressive strength of 2350N / ball, a 2.0m drop strength of 5.5 times / ball, a TFe of 65.1%, a metallization rate of 93.4%, and a dezincification rate of 92.5%.

[0060] The above-described embodiments are only preferred embodiments of the present invention, but not all feasible embodiments of the present invention. For those skilled in the art, any obvious changes made thereto without departing from the principles and spirit of the present invention should be considered to be included in the scope of protection of the claims of the present invention.

Claims

1. A method for comprehensive utilization of zinc-containing dust in steel mills, characterized in that: The following steps are involved: Step 1: Raw material preparation Prepare iron-containing dust, gelatinized starch, bentonite, quicklime and limonite, and grind the limonite finely; Step 2: Make the ingredients into balls The iron-containing dust prepared in step 1, gelatinized starch, bentonite, quicklime and limonite are mixed according to the dry material weight ratio, containing 47% to 62% iron dust, 40% to 45% limonite, 0.8% to 1.5% gelatinized starch, 0.7% to 1.0% bentonite, and 1.0% to 1.4% quicklime, so that the iron grade of the raw pressed mass is ≥53.0%, and the C content of the raw pressed mass is 3.5% to 4.0%, and then pressed under an external pressure of 90MPa to 100MPa; Step 3: High temperature calcination The pressed mass obtained in step 2 is dried and then roasted at a temperature of 1000°C to 1100°C for 10 to 25 minutes. Nitrogen is introduced during the roasting process and the generated smoke is collected. After the roasting, the pressed mass is taken out and cooled in nitrogen to obtain a metallized mass.

2. A method for comprehensive utilization of zinc-containing dust in a steel plant as claimed in claim 1, characterized in that: The iron-containing dust in step 1 includes converter dust, blast furnace raw material ash, blast furnace dry process ash, blast furnace gas ash, and steelmaking secondary dust.

3. A method for comprehensive utilization of zinc-containing dust in a steel plant as claimed in claim 1, characterized in that: The specific surface area of ​​the limonite after fine grinding in step 1 is ≥ 1200 cm 2 / g.

4. A method for comprehensive utilization of zinc-containing dust in a steel plant as claimed in claim 1, characterized in that: The iron-containing dust in step 2 includes 20% to 25% of converter mud, 12% to 15% of blast furnace raw material ash, 10% to 12% of blast furnace dry process ash, 3% to 7% of blast furnace gas ash, and 2% to 3% of steelmaking secondary dust.

5. A method for comprehensive utilization of zinc-containing dust in a steel plant as claimed in claim 1, characterized in that: The outer dimensions of the pressed mass in step 2 are: 30 mm in diameter and 20 mm in height.

6. A method for comprehensive utilization of zinc-containing dust in a steel plant as claimed in claim 1, characterized in that: The pressed balls in step 2 have the following strength parameters: drop strength ≥ 5.0 times / 0.5m, compressive strength ≥ 200N / ball.

7. A method for comprehensive utilization of zinc-containing dust in a steel plant as claimed in claim 1, characterized in that: The metallized agglomerate described in step 3 has a compressive strength of ≥2250 N / ball, a 2.0 m drop strength of ≥6 times / ball, a TFe of ≥63.0%, a metallization rate of ≥92.58%, and a dezincification rate of ≥92.0%.

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