Iron and zinc-containing raw material pellet and preparation method thereof

Abstract

The present application relates to a kind of raw material pellets of iron-containing zinc-containing material and preparation method;The raw material pellet includes iron-containing zinc-containing material, tar residue powder, bentonite, calcium chloride solution and water, and the iron-containing zinc-containing material includes the dust and / or sludge of iron-containing zinc-containing material generated in steel smelting production.This application adopts tar residue powder, iron-containing zinc-containing material, bentonite to prepare layered raw material pellet, realizes the synergistic treatment of tar residue powder and iron-containing zinc-containing material, to waste, the liquid phase component and viscosity of tar residue powder can provide bonding effect and better dispersibility when balling, ensure the strength of raw material pellet, it is favorable for the better formation of second balling wrapping layer, the dispersion degree between materials is better;And calcium chloride is added in the present application, zinc volatilization will form zinc chloride with lower boiling point in the chemical reaction process, improve the dezincification rate of iron-containing zinc-containing material.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment technology, and in particular to a raw material pellet of iron- and zinc-containing materials and its preparation method. Background Technology

[0002] Iron- and zinc-containing dust and / or sludge are high-iron dust and / or sludge generated during iron and steel smelting. They contain usable zinc, iron, and carbon, but due to the high zinc content, direct entry into the blast furnace without release treatment can affect operational stability and lead to zinc accumulation. Currently, the main treatment method for iron- and zinc-containing dust and sludge is rotary hearth furnace or rotary kiln technology. The specific steps are as follows: the iron- and zinc-containing dust and sludge are mixed with carbon powder and additives to form carbon-containing pellets. These pellets are then roasted at high temperature (>1000℃) in a rotary hearth furnace or rotary kiln. During roasting, metallic zinc volatilizes directly, and iron oxides are reduced, ultimately yielding dezincified metallized iron pellets that can directly enter the main sintering process. The removed zinc mainly exists in the form of oxides and can be sold directly. The key factor determining the economic viability of this technology is the zinc removal efficiency. Currently, in industrial production, the zinc removal rate of iron- and zinc-containing dust and sludge is ≥85%, indicating room for improvement. Summary of the Invention

[0003] To address the aforementioned problems, on one hand, the present invention provides a raw material pellet of iron and zinc containing materials, including iron and zinc containing materials, tar residue powder, bentonite, calcium chloride solution and water, wherein the iron and zinc containing materials include iron and zinc containing dust and / or sludge generated in iron and steel smelting production.

[0004] On the other hand, the present invention also provides a method for preparing the above-mentioned iron- and zinc-containing raw material pellets, comprising the following steps:

[0005] S1: A certain amount of iron- and zinc-containing materials, bentonite, tar residue powder and calcium chloride solution are mixed and stirred evenly in a mixer to obtain the first mixture.

[0006] S2: A certain amount of iron- and zinc-containing materials, bentonite, tar residue powder and water are mixed and mixed evenly in a mixer to obtain a second mixture.

[0007] S3: The first mixture is processed into core pellets using the first disc pelletizing process, and the core pellets are then screened.

[0008] S4: After the core pellets are screened, they are sprayed into water and mixed with the second mixture through the second disc pelletizing process to produce raw material pellets with the core pellets as the core particle size.

[0009] Further, in step S1, the content of the tar residue powder is 40-60 wt.% of the iron- and zinc-containing materials, the content of the bentonite is 3-8 wt.% of the iron- and zinc-containing materials, and the content of the calcium chloride solution is 10-20 wt.% of the total amount of the iron- and zinc-containing materials, tar residue powder, and bentonite.

[0010] Specifically, step S1 is the first pelletizing, and step S2 is the second pelletizing. In step S1, the content of tar residue powder, bentonite, and calcium chloride solution is based on the iron- and zinc-containing materials in the first mixture. In step S2, the content of tar residue powder, bentonite, and calcium chloride solution is based on the iron- and zinc-containing materials in the second mixture.

[0011] Further, in step S1, the iron- and zinc-containing materials include the following components by mass percentage of the total iron- and zinc-containing materials: 15-40 wt.% iron concentrate, 15-40 wt.% blast furnace bag ash, and 20-60 wt.% steelmaking ash.

[0012] Specifically, in step S1, the content of each component in the iron- and zinc-containing materials is based on the iron- and zinc-containing materials in the first mixture; in step S2, the content of each component in the iron- and zinc-containing materials is based on the iron- and zinc-containing materials in the second mixture.

[0013] Further, in step S2, the content of the tar residue powder is 10-20 wt.% of the iron- and zinc-containing materials, the content of the bentonite is 3-8 wt.% of the iron- and zinc-containing materials, and the content of water is 10-20 wt.% of the total amount of the iron- and zinc-containing materials, tar residue powder, and bentonite.

[0014] Further, in step S2, the iron- and zinc-containing materials include the following components by mass percentage of the total iron- and zinc-containing materials: 20-40 wt.% iron concentrate, 30-40 wt.% blast furnace bag ash, and 20-30 wt.% steelmaking ash.

[0015] Further, in step S1, the concentration of calcium chloride in the calcium chloride solution is 25-50 wt.%.

[0016] Furthermore, in step S4, the amount of water sprayed is 1 to 2 wt.% of the total amount of the first mixture and the second mixture.

[0017] Furthermore, the ratio of the content of tar residue powder in the second mixture in step S2 to the content of tar residue powder in the first mixture in step S1 is 1:2 to 3.

[0018] Preferably, in the second pelletizing process, the ratio of the content of tar residue powder in the second mixture to the content of tar residue powder in the first mixture in the first pelletizing process is 1:2 to 3.

[0019] Furthermore, in step S3, the particle size of the core pellets is 2-4 mm, and in step S4, the particle size of the raw material pellets is 8-10 mm.

[0020] By employing the above technical solutions, this invention has the following advantages compared to existing technologies:

[0021] 1) The raw material pellets containing iron and zinc provided by this invention and their preparation method use tar residue powder, iron and zinc-containing materials, and bentonite to prepare layered raw material pellets, realizing the synergistic treatment of tar residue powder and iron and zinc-containing materials, turning waste into waste. The liquid phase components and viscosity of tar residue powder can provide a binding effect and better dispersibility during pelleting, ensuring the strength of the raw material pellets, which is conducive to the better formation of the second pelleting coating layer and the better dispersion between materials. In addition, calcium chloride is added in this application, and zinc chloride with a lower boiling point will be formed during the chemical reaction of zinc volatilization, thereby improving the dezincification rate.

[0022] 2) The iron- and zinc-containing raw material pellets and their preparation method provided by this invention form two raw material pellet structures with different inner and outer layers. The carbon content in the core pellet is 20% to 40% of the core pellet, and the carbon content in the coating layer covering the core pellet is 6% to 16% of the coating layer. The difference in carbon content, which is higher inside and lower outside, helps to maintain a higher CO concentration inside the raw material pellet, thereby allowing CO to diffuse from the inside to the outside and forming a more uniform reducing atmosphere inside and outside, thus strengthening the chemical reaction kinetics of the dezincification process. Attached Figure Description

[0023] Figure 1 A flowchart illustrating the method for preparing raw material pellets containing iron and zinc provided by the present invention;

[0024] Figure 2 This is a schematic diagram of the structure of raw material pellets containing iron and zinc provided by the present invention. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0026] This invention provides a raw material pellet of iron and zinc containing materials, including iron and zinc containing materials, tar residue powder, bentonite and calcium chloride solution, wherein the iron and zinc containing materials include iron and zinc containing dust and / or sludge generated in iron and steel smelting production.

[0027] This invention also provides a method for preparing raw material pellets containing iron and zinc as described above, as shown in the appendix to the specification. Figure 1 The diagram shown is a flowchart of the preparation process, which includes the following steps:

[0028] S1: A certain amount of iron- and zinc-containing materials, bentonite, tar residue powder and calcium chloride solution are mixed and stirred evenly in a mixer to obtain the first mixture.

[0029] Preferably, the iron- and zinc-containing materials include iron concentrate, blast furnace bag ash, and steelmaking ash. The iron- and zinc-containing materials, bentonite, and tar residue powder are mixed together, and calcium chloride solution is added. The mixture is then stirred in a first high-power mixer for 1 to 3 minutes to obtain a first mixture. The stirred first mixture is then sent to a first pelletizing buffer silo for temporary storage.

[0030] S2: A certain amount of iron- and zinc-containing materials, bentonite, tar residue powder and water are mixed and mixed evenly in a mixer to obtain a second mixture.

[0031] Preferably, the iron- and zinc-containing materials include iron concentrate, blast furnace bag ash, and steelmaking ash. The iron- and zinc-containing materials, bentonite, and tar residue powder are mixed with water and fed into a second high-strength mixer for uniform mixing. The mixing time is 1 to 3 minutes to obtain a second mixture. The uniformly mixed second mixture is then sent to a second pelletizing buffer silo for temporary storage.

[0032] S3: The first mixture is processed into core pellets using the first disc pelletizing process, and the core pellets are then screened.

[0033] Preferably, a disc pelletizer is used for pelletizing. The first mixture in the first pelletizing buffer chamber is sent to the first disc pelletizer for pelletizing. The rotation speed and tilt angle of the first disc pelletizer are controlled to obtain core pellets.

[0034] The core pellets are passed through a large ball roller to remove small balls with a diameter greater than 4 mm, and then through a small ball roller to remove small balls with a diameter less than 2 mm. After screening, core pellets with a diameter of 2 to 4 mm are obtained.

[0035] The small balls with a particle size greater than 4 mm and a particle size less than 2 mm that are screened out can be returned to the first disc pelletizer for recycling.

[0036] S4: After the core pellets are screened, they are sprayed into water and mixed with the second mixture through the second disc pelletizing process to produce raw material pellets with the core pellets as the core particle size.

[0037] Preferably, the core pellets screened in step S3 are sent to the second disc pelletizer, a certain amount of water is sprayed in, and then the second mixture in the second pelletizing buffer chamber is sent to the second disc pelletizer to continue growing with the core pellets as the mother nucleus. The rotation speed and tilt angle of the second disc pelletizer are controlled to obtain raw material pellets.

[0038] Preferably, the above-mentioned raw material pellets are passed through a large ball roller to remove small pellets with a particle size exceeding 10 mm, and then through a small ball roller to remove small pellets with a particle size less than 8 mm. After screening, raw material pellets with a particle size of 8-10 mm are obtained; as per the attached instruction manual. Figure 2 The diagram shows the structure of raw material pellets. Through multiple pelletizing processes, two layers of raw material pellets with different compositions are obtained. The inner layer is the core pellet 1 with a particle size of 2-4 mm. The outer coating layer 2 coats the core pellet to form the raw material pellets with a particle size of 8-10 mm.

[0039] The small balls with a particle size greater than 10 mm and a particle size less than 8 mm that are screened out can be returned to the second disc pelletizer for recycling.

[0040] Preferably, the preparation process of tar residue powder in steps S1 and S2 is as follows: the tar by-product of the coking process is separated from the oil residue and dried to obtain tar residue. The tar residue is then sieved through a cylindrical roller screen to obtain tar residue powder with a particle size of <0.5mm for later use. Specifically, the content of solid matter (such as fixed carbon, ash, etc.) in the tar residue powder is ≥70%, and the content of liquid components (such as water, oil, etc.) is <30%.

[0041] Preferably, the steelmaking ash in steps S1 and S2 is the steelmaking ash after dissolution.

[0042] This application adds calcium chloride. During the chemical reaction of zinc volatilization, zinc chloride with a lower boiling point will be formed. Increasing the calcium chloride content will help remove zinc and increase the zinc removal rate of iron- and zinc-containing materials. However, it is also necessary to control the calcium chloride content to ensure that the chlorine has little corrosive effect on the equipment and does not affect the quality of zinc powder.

[0043] Example 1

[0044] S1: Take 520g of iron concentrate, 400g of blast furnace bag ash, and 1000g of digested steelmaking ash and pour them into the mixer. Then take 1000g of tar residue powder and 100g of bentonite and pour them into the mixer. After starting the mixer, pour in 434g of calcium chloride solution. The calcium chloride concentration in the calcium chloride solution is 30wt.%. After stirring for 2 minutes, the first mixture is obtained for later use.

[0045] S2: Take 3640g of iron concentrate, 2800g of blast furnace bag ash, and 7000g of digested steelmaking ash and pour them into the mixer. Then take 1400g of tar residue powder and 700g of bentonite and pour them into the mixer. After starting the mixer, pour in 2254g of water and stir for 2 minutes to obtain the second mixture for later use.

[0046] S3: The first mixture is fed into the first disc pelletizer to form pellets, and after passing through the large and small ball rollers in sequence, core pellets with a particle size of 2-4 mm are obtained by screening.

[0047] S4: The core pellets with a particle size of 2-4 mm are fed into the second disc pelletizer and 217 g of water is sprayed in. Then, the second mixture is poured into the second disc pelletizer to form pellets. After passing through the large and small ball rollers in sequence, raw material pellets with a particle size of 8-10 mm are obtained by screening.

[0048] Example 2

[0049] S1: Take 600g of iron concentrate, 400g of blast furnace bag ash, and 1000g of digested steelmaking ash and pour them into the mixer. Then take 800g of tar residue powder and 100g of bentonite and pour them into the mixer. After starting the mixer, pour in 400g of calcium chloride solution. The calcium chloride concentration in the calcium chloride solution is 30wt.%. After stirring for 2 minutes, the first mixture is obtained for later use.

[0050] S2: Take 4200g of iron concentrate, 2800g of blast furnace bag ash, and 7000g of digested steelmaking ash and pour them into the mixer. Then take 1750g of tar residue powder and 700g of bentonite and pour them into the mixer. After starting the mixer, pour in 2100g of water and stir for 2 minutes to obtain the second mixture for later use.

[0051] S3: The first mixture is fed into the first disc pelletizer to form pellets, and after passing through the large and small ball rollers in sequence, core pellets with a particle size of 2-4 mm are obtained by screening.

[0052] S4: The core pellets with a particle size of 2-4 mm are fed into the second disc pelletizer and 217 g of water is sprayed in. Then, the second mixture is poured into the second disc pelletizer to form pellets. After passing through the large and small ball rollers in sequence, raw material pellets with a particle size of 8-10 mm are obtained by screening.

[0053] Example 3

[0054] S1: Take 410g of iron concentrate, 170g of blast furnace bag ash, and 520g of digested steelmaking ash and pour them into the mixer. Then take 520g of tar residue powder and 90g of bentonite and pour them into the mixer. After starting the mixer, pour in 150g of calcium chloride solution. The calcium chloride concentration in the calcium chloride solution is 30wt.%. After stirring for 2 minutes, the first mixture is obtained for later use.

[0055] S2: Take 2940g of iron concentrate, 1120g of blast furnace bag ash, and 3640g of digested steelmaking ash and pour them into the mixer. Then take 1400g of tar residue powder and 630g of bentonite and pour them into the mixer. After starting the mixer, pour in 1050g of water and stir for 2 minutes to obtain the second mixture for later use.

[0056] S3: The first mixture is fed into the first disc pelletizer to form pellets, and after passing through the large and small ball rollers in sequence, core pellets with a particle size of 2-4 mm are obtained by screening.

[0057] S4: The core pellets with a particle size of 2-4 mm are fed into the second disc pelletizer and 217 g of water is sprayed in. Then, the second mixture is poured into the second disc pelletizer to form pellets. After passing through the large and small ball rollers in sequence, raw material pellets with a particle size of 8-10 mm are obtained by screening.

[0058] Example 4

[0059] S1: Take 320g of iron concentrate, 160g of blast furnace bag ash, and 500g of digested steelmaking ash and pour them into the mixer. Then take 400g of tar residue powder and 80g of bentonite and pour them into the mixer. After starting the mixer, pour in 150g of calcium chloride solution. The calcium chloride concentration in the calcium chloride solution is 20wt.%. After stirring for 2 minutes, the first mixture is obtained for later use.

[0060] S2: Take 2100g of iron concentrate, 1120g of blast furnace bag ash, and 3640g of digested steelmaking ash and pour them into the mixer. Then take 1400g of tar residue powder and 560g of bentonite and pour them into the mixer. After starting the mixer, pour in 1050g of water and stir for 2 minutes to obtain the second mixture for later use.

[0061] S3: The first mixture is fed into the first disc pelletizer to form pellets, and after passing through the large and small ball rollers in sequence, core pellets with a particle size of 2-4 mm are obtained by screening.

[0062] S4: The core pellets with a particle size of 2-4 mm are fed into the second disc pelletizer and 217 g of water is sprayed in. Then, the second mixture is poured into the second disc pelletizer to form pellets. After passing through the large and small ball rollers in sequence, raw material pellets with a particle size of 8-10 mm are obtained by screening.

[0063] The raw material pellets obtained in Examples 1-4 were tested after being metallized in a rotary hearth furnace. The results are as follows:

[0064] Metallization rate Zinc removal rate raw material compressive strength Example 1 92.1％ 96.0％ 16.4N Example 2 94.7％ 97.0％ 16.0N Example 3 95.0％ 97.2％ 16.4N Example 4 94.2％ 96.5％ 15.5N

[0065] The test results show that the raw pellets obtained by the preparation method of this application, after being metallized in a rotary hearth furnace, have a metal conversion rate of >92%, a zinc removal rate of >95%, and a raw compressive strength of >15N.

[0066] Those skilled in the art will understand that the present invention can be implemented in many other specific forms without departing from the spirit and scope of the invention. Although embodiments of the invention have been described, it should be understood that the invention is not limited to these embodiments, and those skilled in the art can make changes and modifications within the spirit and scope of the invention as defined in the appended claims.

Claims

1. A raw material pellet containing iron and zinc, characterized in that, It includes iron- and zinc-containing materials, tar residue powder, bentonite, calcium chloride solution, and water. The iron- and zinc-containing materials include iron- and zinc-containing dust and / or sludge generated during iron and steel smelting production. The method for preparing the iron- and zinc-containing raw material pellets includes the following steps: S1: A certain amount of iron- and zinc-containing materials, bentonite, tar residue powder and calcium chloride solution are mixed and stirred evenly in a mixer to obtain the first mixture. S2: A certain amount of iron- and zinc-containing materials, bentonite, tar residue powder and water are mixed and stirred evenly in a mixer to obtain a second mixture. S3: The first mixture is processed into core pellets using the first disc pelletizing process, and the core pellets are then screened. S4: After the core pellets are sprayed into water, they are mixed with the second mixture and processed by the second disc pelletizing process to produce raw pellets with the core pellets as the core particle size. Wherein, the content of tar residue powder in the second mixture in step S2 and the content of tar residue powder in the first mixture in step S1 are in the ratio of 1:2~3; The carbon content in the core pellet is 20% to 40% of the core pellet, and the carbon content in the coating layer covering the core pellet is 6% to 16% of the coating layer.

2. The iron- and zinc-containing raw material pellets as described in claim 1, characterized in that, In step S1, the content of the tar residue powder is 40-60 wt.% of the iron- and zinc-containing materials, the content of the bentonite is 3-8 wt.% of the iron- and zinc-containing materials, and the content of the calcium chloride solution is 10-20 wt.% of the total amount of the iron- and zinc-containing materials, tar residue powder, and bentonite.

3. The iron- and zinc-containing raw material pellets as described in claim 1, characterized in that, In step S1, the iron- and zinc-containing materials include the following components by the total mass percentage of the iron- and zinc-containing materials: 15-40 wt.% iron concentrate, 15-40 wt.% blast furnace bag ash, and 20-60 wt.% steelmaking ash.

4. The iron- and zinc-containing raw material pellets as described in claim 1, characterized in that, In step S2, the content of the tar residue powder is 10-20 wt.% of the iron- and zinc-containing materials, the content of the bentonite is 3-8 wt.% of the iron- and zinc-containing materials, and the content of water is 10-20 wt.% of the total amount of the iron- and zinc-containing materials, tar residue powder, and bentonite.

5. The iron- and zinc-containing raw material pellets as described in claim 1, characterized in that, In step S2, the iron- and zinc-containing materials include the following components by the total mass percentage of the iron- and zinc-containing materials: 20-40 wt.% iron concentrate, 30-40 wt.% blast furnace bag ash, and 20-30 wt.% steelmaking ash.

6. The iron- and zinc-containing raw material pellets as described in claim 1, characterized in that, In step S1, the concentration of calcium chloride in the calcium chloride solution is 25~50 wt.%.

7. The iron- and zinc-containing raw material pellets as described in claim 1, characterized in that, In step S4, the amount of water sprayed is 1 to 2 wt. of the total amount of the first mixture and the second mixture.

8. The iron- and zinc-containing raw material pellets as described in claim 1, characterized in that, In step S3, the core pellet has a particle size of 2-4 mm, and in step S4, the raw material pellet has a particle size of 8-10 mm.

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