Converter steel slag tailing resintering utilization method

Abstract

The application discloses a converter steel slag tailing sintering utilization method, wherein steel slag tailing with a particle size range of 0-10 mm is air-dried for 5-10 days to reduce the water content to below 7%; the air-dried steel slag tailing is further classified into steel slag tailing with a particle size of >5 mm and <5 mm; the steel slag tailing with a particle size of <5 mm is dried to a water content of below 2% and is sent to a ball mill to be ground into steel slag tailing with a particle size of <3 mm; after magnetic separation, non-magnetic steel slag tailing with a particle size of <3 mm is obtained and is uniformly mixed with biomass fuel at a mass ratio of (18-20):1; the obtained steel slag tailing with a particle size of >5 mm, the non-magnetic steel slag tailing obtained in step (3) and the biomass fuel mixture, mixed ore, sintering flux, return ore and fuel are fully mixed at a proper ratio to obtain sintering mixture for producing sintered ore; the application overcomes the adverse effects of adding steel slag in the sintering process and has the product advantages of high strength, low energy consumption and low cost compared with conventional methods; and the application provides a method for recycling converter steel slag tailing.

Description

A method for recycling converter steel slag tailings through sintering Technical Field

[0001] This invention belongs to the field of solid waste treatment technology, specifically relating to a method for the recycling and sintering of converter steel slag tailings. Background Technology

[0002] In recent years, due to a sluggish market and declining steel demand, coupled with rising raw material costs for sintering, the steel industry has been operating under a pattern of high costs, low prices, and low profits. Faced with the dual challenges of profitability and environmental protection, optimizing existing resource allocation and achieving efficient recycling of secondary resources are effective ways to overcome the current predicament.

[0003] Converter slag is a byproduct of steelmaking, accounting for approximately 15% of crude steel production. Typically, converter slag undergoes crushing, screening, and magnetic separation to recover metals, resulting in steel slag tailings with a particle size of 0-10mm. This waste is generally used as building materials or in cement, but its addition is limited due to factors such as iron content and instability. Furthermore, in 2021, the national standard GB 175 "General Portland Cement" for the cement industry was revised, excluding steel slag tailings from the list of raw materials for cement admixtures. This has led to difficulties in the co-processing of steel slag tailings in the cement industry, resulting in a significant decrease in demand. Therefore, research on the resource utilization technology of steel slag tailings is urgently needed to expand its utilization pathways.

[0004] Reports of steel slag re-sintering were published in the early 1970s. However, the re-sintering process is prone to problems such as uneven steel slag particle size reducing the permeability of sinter and unstable composition affecting sintering batching and sintering control. With the continuous development of sintering technology and steel slag tailings preparation technology, a high-value-added method for steel slag re-sintering is still urgently needed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for the re-sintering and utilization of converter steel slag tailings, which overcomes the adverse effects of adding steel slag during the sintering process and has product advantages such as high strength, low energy consumption, and low cost compared with conventional methods; at the same time, it provides a method for the resource utilization of converter steel slag tailings.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] A method for recycling converter steel slag tailings through sintering includes the following steps:

[0008] (1) Natural dehydration;

[0009] Steel slag tailings with a particle size range of 0-10 mm are air-dried for 5-10 days to reduce their moisture content to below 7%.

[0010] (2) Screening;

[0011] The air-dried steel slag tailings were further screened into two particle sizes: >5mm and <5mm.

[0012] (3) Ball milling for iron selection;

[0013] The steel slag tailings with a diameter of <5mm are dried to a moisture content of less than 2%, and then fed into a ball mill to be ground into steel slag tailings with a diameter of <3mm. After magnetic separation, non-magnetic steel slag tailings with a diameter of <3mm are obtained. The obtained non-magnetic steel slag tailings are mixed with biomass fuel at a mass ratio of (18-20):1.

[0014] (4) Tailings slag is recycled and reused in a cascade manner;

[0015] The steel slag tailings >5mm obtained in step (2), the non-magnetic steel slag tailings obtained in step (3), the biomass fuel mixture, the blended ore, the sintering flux, the return ore, and the fuel are fully mixed in proportion to obtain a sintering mixture for use in the production of sintered ore.

[0016] According to the above scheme, the screening process in step (2) is completed by a square-hole vibrating screen.

[0017] According to the above scheme, the drying process in step (3) is completed using a drum dryer.

[0018] According to the above scheme, the magnetic separation process in step (3) uses dry electromagnetic separation with a magnetic induction intensity of 800 Gbs.

[0019] According to the above scheme, the biomass fuel in step (3) is any mixture of stem crops, peanut shells, bark, and sawdust, with a calorific value of 14.6 J / G or higher, and is processed into pellet fuel with a particle size of 4-6 mm.

[0020] According to the above scheme, the sintering flux in step (4) is quicklime, limestone and dolomite.

[0021] According to the above scheme, the fuel in step (4) is anthracite or coke powder.

[0022] According to the above scheme, the sintering mixture in step (4) is calculated as follows by mass percentage:

[0023] >5mm steel slag tailings 1-2%; non-magnetic steel slag tailings mixed with biomass fuel 2-7%; blended ore 55-60%; sintering flux 10-12%; recycled ore 23-27%; fuel 4-5%.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] Compared with the traditional method of directly adding steel slag tailings, the steel slag tailings with a particle size of <3mm after grinding contain a certain amount of magnesium oxide and calcium oxide, which can replace part of the sintering flux and reduce the consumption of sintering fuel; ball milling also makes its chemical composition more uniform and avoids the problem of large fluctuations in alkalinity.

[0026] The addition of steel slag tailings larger than 5mm improves the granulation performance of sintering raw materials and slightly improves the permeability of sintering, which is beneficial for thick material layer sintering and thus increases the hourly output of sintering tables.

[0027] The added biomass fuel can replace part of the sintered fuel, reducing carbon emissions while neutralizing the adverse effects of fine steel slag particles on air permeability.

[0028] The cascade utilization of steel slag tailings can improve sintering efficiency while increasing the proportion of steel slag incorporation to 9%, maximizing the efficient utilization of secondary resources.

[0029] The present invention has a simple process, uses solid waste as raw material, and has significant technical and economic benefits. Attached Figure Description

[0030] Figure 1: Schematic diagram of the method for re-sintering and utilizing converter steel slag tailings of the present invention. Detailed Implementation

[0031] The following embodiments further illustrate the technical solution of the present invention, but are not intended to limit the scope of protection of the present invention.

[0032] A specific implementation provides a method for the recycling of converter steel slag tailings through sintering, including the following steps:

[0033] (1) Natural dehydration: Air dry steel slag tailings with a particle size range of 0-10mm for 5-10 days to reduce their moisture content to below 7%;

[0034] (2) Screening; The air-dried steel slag tailings are further screened into two particle sizes: >5mm and <5mm.

[0035] (3) Ball milling for iron separation; dry the steel slag tailings of <5mm to a moisture content of less than 2%, and send them to a ball mill to be ground into steel slag tailings of <3mm. After magnetic separation, non-magnetic steel slag tailings of <3mm are obtained. The obtained non-magnetic steel slag tailings are mixed with biomass fuel at a mass ratio of 18-20:1.

[0036] (4) Tailings are recycled for sintering in stages; the steel slag tailings >5mm obtained in step (2), the non-magnetic steel slag tailings obtained in step (3), the biomass fuel mixture, the blended ore, the sintering flux, the recycled ore and the fuel are fully mixed in proportion to obtain a sintering mixture for use in the production of sintered ore.

[0037] Specifically, the screening process in step (2) is completed by a square-hole vibrating screen.

[0038] Specifically, the drying process in step (3) is completed using a drum dryer.

[0039] Specifically, in step (3), the magnetic separation process uses dry electromagnetic separation with a magnetic induction intensity of 800 Gbs.

[0040] Specifically, the biomass fuel in step (3) is any mixture of stem crops, peanut shells, bark, and sawdust, with a calorific value of 14.6 J / G or higher, and is processed into pellet fuel with a particle size of 4-6 mm.

[0041] Specifically, the sintering flux in step (4) is quicklime, limestone and dolomite.

[0042] Specifically, the fuel mentioned in step (4) is anthracite or coke powder.

[0043] Specifically, the sintering mixture in step (4) is expressed as a percentage by mass as follows:

[0044] >5mm steel slag tailings 1-2%; non-magnetic steel slag tailings mixed with biomass fuel 2-7%; blended ore 55-60%; sintering flux 10-12%; recycled ore 23-27%; fuel 4-5%.

[0045] Example 1

[0046] (1) Natural dehydration: Steel slag tailings with a particle size range of 0-10mm are piled up in a greenhouse under natural ventilation for 5 days, so that the moisture content drops to 7% after the water vapor evaporates.

[0047] (2) Screening: The air-dried steel slag tailings are further screened into two particle sizes: >5mm and <5mm.

[0048] (3) Ball milling for iron separation: The steel slag tailings <5mm obtained in step (2) are further dried in a drum dryer to a moisture content of less than 2%, and then sent to a ball mill to be ground into steel slag tailings <3mm. The tailings are then subjected to dry electromagnetic separation at a magnetic induction intensity of 800Gbs to obtain non-magnetic steel slag tailings <3mm. The obtained steel slag tailings are then mixed evenly with biomass fuel at a mass ratio of 18:1.

[0049] (4) Tailings return to sintering for cascade utilization: Steel slag tailings >5mm, non-magnetic steel slag tailings, biomass fuel mixture, blended ore, sintering flux, return ore, and fuel are uniformly mixed at mass percentages of 2%, 7%, 54%, 10%, 23%, and 4% respectively to obtain sintering mixture for use in the production of sintered ore.

[0050] Example 2

[0051] (1) Natural dehydration: Steel slag tailings with a particle size range of 0-10mm are piled up in a greenhouse under natural ventilation for 7 days, so that the moisture content drops to 6% after the water vapor evaporates.

[0052] (2) Screening: The air-dried steel slag tailings are further screened into two particle sizes: >5mm and <5mm.

[0053] (3) Ball milling for iron separation: The steel slag tailings <5mm obtained in step (2) are further dried in a drum dryer to a moisture content of less than 2%, and then sent to a ball mill to be ground into steel slag tailings <3mm. The tailings are then subjected to dry electromagnetic separation at a magnetic induction intensity of 800Gbs to obtain non-magnetic steel slag tailings <3mm. The obtained steel slag tailings are then mixed evenly with biomass fuel at a mass ratio of 19:1.

[0054] (4) Tailings return to sintering for cascade utilization: Steel slag tailings >5mm, non-magnetic steel slag tailings, biomass fuel mixture, blended ore, sintering flux, return ore, and fuel are uniformly mixed at mass percentages of 1%, 2%, 57%, 10%, 25%, and 5% respectively to obtain sintering mixture for use in the production of sintered ore.

[0055] Example 3:

[0056] (1) Natural dehydration: Steel slag tailings with a particle size range of 0-10mm are piled up in a greenhouse under natural ventilation for 10 days, so that the moisture content drops to 5% after the water vapor evaporates.

[0057] (2) Screening: The air-dried steel slag tailings are further screened into two particle sizes: >5mm and <5mm.

[0058] (3) Ball milling for iron separation: The steel slag tailings <5mm obtained in step (2) are further dried in a drum dryer to a moisture content of less than 2%, and then sent to a ball mill to be ground into steel slag tailings <3mm. The tailings are then subjected to dry electromagnetic separation at a magnetic induction intensity of 800Gbs to obtain non-magnetic steel slag tailings <3mm. The obtained steel slag tailings are then mixed evenly with biomass fuel at a mass ratio of 20:1.

[0059] (4) Tailings return to sintering for cascade utilization: Steel slag tailings >5mm, non-magnetic steel slag tailings, biomass fuel mixture, blended ore, sintering flux, return ore, and fuel are uniformly mixed at mass percentages of 2%, 4%, 55%, 10.5%, 24%, and 4.5% respectively to obtain sintering mixture for use in the production of sintered ore.

[0060] Comparative Example 1: Repeat Example 1, omitting step 3, while keeping the other steps unchanged.

[0061] Comparative Example 2: Repeat Example 1, in step 3, steel slag tailings <5mm were directly mixed with biomass fuel.

[0062] Comparative Example 3: Repeat Example 1, but without adding biomass fuel in step 3.

[0063] The sintering index results of Examples 1-3 and Comparative Examples 1-3 are shown in Table 1 below.

[0064] Table 1

[0065]

[0066] The test results show that the recycling of steel slag for sintering production reduces fuel consumption while increasing the strength of the sinter. Since steel slag with a particle size of 3mm-5mm cannot replace iron ore to provide high-grade Fe, nor can it replace flux to provide high-grade MgO and CaO, it also reduces the strength of the sinter. Magnetic separation can more efficiently recover Fe from steel slag. The addition of biomass fuel reduces fuel consumption while further increasing the permeability and sintering strength of the bed. On the other hand, based on the chemical composition analysis of the steel slag, with a total iron (TFe) content of approximately 22%, compared to the domestic price of 500 yuan / ton for low-priced iron concentrate with an iron grade of 58%, the economic benefit of recovering iron from steel slag tailings, directly converted based on its content, is approximately 189 yuan / ton. Therefore, compared to traditional methods, this invention has the advantages of high strength, low energy consumption, and low cost.

Claims

1. A method for utilizing converter steel slag tailings through sintering, characterized in that... Includes the following steps: (1) Air-dry steel slag tailings with a particle size range of 0-10 mm for 5-10 days to reduce their moisture content to below 7%; (2) Further screen the air-dried steel slag tailings into two particle sizes: >5 mm and <5 mm; (3) Dry the <5 mm steel slag tailings to a moisture content of below 2%, and then grind them into <3 mm steel slag tailings in a ball mill. After magnetic separation, obtain <3 mm non-magnetic steel slag tailings. Mix the obtained non-magnetic steel slag tailings with biomass fuel at a mass ratio of (18-20):1; (4) Mix the >5 mm steel slag tailings obtained in step (2), the non-magnetic steel slag tailings obtained in step (3), and the biomass fuel, and then mix them with the ore. Sintering flux, recycled ore, and fuel are thoroughly mixed in proportion to obtain a sintering mixture for use in the production of sintered ore. The biomass fuel is any mixture of stalk crops, peanut shells, bark, and sawdust, with a calorific value of 14.6 J / G or higher, and processed into granular fuel with a particle size of 4-6 mm. The sintering flux is quicklime, limestone, and dolomite. The fuel is anthracite and coke powder. The sintering mixture, by mass percentage, is as follows: >5 mm steel slag tailings 1-2%; a mixture of non-magnetic steel slag tailings and biomass fuel 2-7%; blended ore 55-60%; sintering flux 10-12%; recycled ore 23-27%; and fuel 4-5%.

2. The method for recycling converter steel slag tailings as described in claim 1, characterized in that... The screening process in step (2) is completed by a square-hole vibrating screen.

3. The method for recycling converter steel slag tailings as described in claim 1, characterized in that... Step (3) The drying process is completed using a drum dryer.

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