A method for grading and efficient resource utilization of converter steel slag

Abstract

The application discloses a kind of converter steel slag grading efficient resource utilization method, comprising the following steps: (1) converter steel slag pretreatment, liquid converter steel slag is sequentially crushed by rolling, hot stew under pressure, rod grinding and impurity removal process to obtain pretreated steel slag;(2) grading screening, pretreated steel slag is graded using a mobile five-layer vibrating screen;(3) product adaptation treatment, 16-63mm products are used as railway ballast;5-10mm, 10-15mm products are used as road asphalt surface layer aggregate;<8 mesh products are used as steel slag sand for rust removal (4) wastewater, dust treatment and metal, waste heat recovery treatment.The application greatly improves the processing efficiency, significantly enhances the stability of the product, has outstanding environmental performance, optimizes waste heat utilization and energy consumption, has high resource utilization rate and added value, and has significant social benefits.

Description

Technical Field

[0001] This invention relates to the field of steel slag treatment technology, specifically to a method for efficient resource utilization of converter steel slag through grading. Background Technology

[0002] Converter slag, a core solid byproduct generated during converter steelmaking, accounts for approximately 13% to 15% of crude steel production. Existing technologies for the resource utilization of converter slag suffer from several critical shortcomings, hindering the achievement of comprehensive, high-value, and clean utilization. Specifically: 1. Liquid steel slag treatment is inefficient and environmentally unfriendly: Traditional processes often use atmospheric pressure pool hot quenching (treatment cycle up to 24 hours), air quenching or hot pouring treatment, which results in the free CaO content in the steel slag generally exceeding 5%. In subsequent applications, hydration expansion reaction is likely to occur, causing product cracking, failure and other quality hazards. Moreover, the atmospheric pressure treatment system is in an open or semi-open state, and dust and harmful gases are released without organization during the treatment process, which seriously does not meet the current environmental emission requirements.

[0003] 2. Insufficient adaptability of crushing and cooling: Traditional crushing devices fail to match the multiphase characteristics of molten steel slag, resulting in slow cooling rates (it takes more than 1 hour to cool from 1600℃ to 600℃). The steel slag particles after crushing are uneven in size (mostly larger than 300mm), which not only increases the energy consumption burden of subsequent processing but also affects the stability of product quality.

[0004] 3. Disconnect between particle size classification and application scenarios: The application of the technology is mostly limited to low-value scenarios such as road fillers and cement admixtures, and does not cover high-value-added fields such as railway ballast. Even when used in road construction, it is not accurately classified according to specific standards, which results in the inability to fully utilize the performance advantages of steel slag aggregate, and insufficient adaptability and practicality.

[0005] 4. Lack of high-value utilization pathways: More than 80% of converter steel slag is only used as low-cost filler. The core characteristics of its steel slag sand, such as high hardness and excellent angularity, have not been deeply explored and have not been effectively extended to high-value application scenarios such as rust removal abrasives. The resource value is seriously underestimated.

[0006] 5. Insufficient utilization of components: The Fe2O3 content in converter steel slag is as high as 30% to 45%, which is a high-quality raw material for correcting iron in cement. However, due to the lack of targeted crushing and purification processes, the utilization rate of this component is less than 20%, and a large amount of iron resources are wasted, failing to achieve full resource utilization of all components.

[0007] 6. Significant energy waste: In traditional processes, steel slag drying relies on external heat sources (such as coal and electricity), failing to effectively recover the large amount of waste heat resources released during the liquid steel slag treatment process, resulting in low energy utilization and further increasing resource recovery costs.

[0008] In summary, existing technologies cannot solve the multiple problems of low efficiency in converter steel slag treatment, poor product stability, narrow high-value-added pathways, and failure to meet environmental protection and energy consumption standards. There is an urgent need to develop a closed-loop resource utilization technology that integrates precise pretreatment of liquid steel slag, full particle size classification, multi-scenario targeted modification, and waste heat recovery and utilization to break through the industry's development dilemma. Summary of the Invention

[0009] The purpose of this invention is to provide a method for efficient resource utilization of converter steel slag through grading, which solves the core problems of poor adaptability, low added value, potential risks of hydration expansion of free calcium oxide and free magnesium oxide, and resource waste in existing converter steel slag utilization.

[0010] To achieve the above objectives, the present invention provides the following technical solution: a method for efficient resource utilization of converter steel slag through classification, comprising the following steps: (1) Pretreatment of converter steel slag Liquid converter slag is sequentially subjected to roller crushing, pressurized hot curing, rod milling, and impurity removal processes to obtain pretreated slag. The roller crushing time is 20-30 minutes, and the crushed particle size is ≤300mm. During the crushing process, cold air is introduced for heat exchange. The hot air is converted into hot air for subsequent drying after dust removal by a high-temperature bag filter. The liquid slag is cooled and solidified at a temperature of 500-600℃. Pressurized hot curing is carried out in a sealed tank. Water is injected into the tank, and a large amount of water vapor is generated using the residual heat of the slag. The working pressure is maintained at 0.2-0.4MPa for at least 1 hour. The rod milling is performed to a particle size of ≤63mm to remove the loose surface layer and large particles that have not been fully reacted. The impurity removal process uses a 63mm aperture drum screen combined with manual removal to remove refractory materials and scrap steel blocks with a diameter ≥63mm. Finally, pretreated slag with a purity ≥95% and free CaO ≤2.0% is obtained. (4) Grading and screening A mobile five-layer vibrating screen was used to classify the pretreated steel slag. The vibration frequency of the vibrating screen was 1200-1500 r / min, the amplitude was 5-8 mm, and the screen mesh size from top to bottom was 63 mm, 15 mm, 10 mm, 5 mm, and 8 mesh, which separated converter steel slag products of 16-63 mm, 10-15 mm, 5-10 mm, and <8 mesh in sequence. (3) Product adaptation treatment After iron removal, screening, grading, and compressive strength testing of the 16-63mm product using a permanent magnet drum magnetic separator, it is used as railway ballast. The magnetic field strength of the permanent magnet drum magnetic separator is 8000-10000Gs, and the 31.5-63mm product accounts for ≥95%. The 5-10mm and 10-15mm steel slag aggregates, after being treated with a wet magnetic separator for iron removal, washing, drying, and gradation adjustment, are used as aggregates for road asphalt surface courses. The magnetic field strength of the wet magnetic separator is 10000-15000 Gs, the washing pressure is 0.3-0.5 MPa, and the drying process uses hot air from a crushing process at a temperature of 300-350℃. After gradation adjustment, the 5-10mm steel slag aggregate meets the following requirements: 100% passing rate on a 13.2mm square hole sieve, greater than 90% passing rate on a 9.5mm square hole sieve, less than 10% passing rate on a 4.75mm square hole sieve, and less than 5% passing rate on a 2.36mm square hole sieve; the 10-15mm steel slag aggregate meets the following requirements: 100% passing rate on a 16mm square hole sieve, greater than 90% passing rate on a 13.2mm square hole sieve, less than 15% passing rate on a 9.5mm square hole sieve, and less than 5% passing rate on a 4.75mm square hole sieve. The product with a mesh size <8 is dried by hot air after crushing and conversion, and then mechanically hardened and graded. It is then used as steel slag sand for rust removal. The hot air temperature is 300-350℃ and the drying time is 2-3 hours. The product with a mesh size <20 is then screened out. The product with a mesh size of <20 mesh is ball-milled and then subjected to iron removal by a vertical ring high gradient magnetic separator. It is then pulverized to a mesh size of ≥90% and used as a raw material for correcting iron content in cement. The ball milling time is 3-4 hours and the magnetic field strength of the vertical ring high gradient magnetic separator is 8000-10000 Gs. (4) Wastewater and dust treatment and metal and waste heat recovery treatment Wastewater generated from washing is treated sequentially through sedimentation tanks, filters, and pH adjustment tanks before being recycled for the washing process. Dust generated during screening, crushing, and rod milling is collected by a high-temperature bag filter and then mixed into cement raw materials for reuse, achieving dust-free emissions. Metals recovered by magnetic separators in each process are returned to the steel plant for remelting. The conversion hot air generated during crushing is allocated according to the heat requirements of road asphalt surface aggregates and rust-removing steel slag sand, and used for the drying processes of these two types of materials respectively.

[0011] Preferably, in step (1), the pressurized hot braising time is 1.5 to 2 hours, and the hot braising process is completely sealed, with the air leakage rate of the sealed tank ≤0.5%.

[0012] Preferably, in step (1), the media filling rate of the rod mill used in the rod mill is 60% to 70%.

[0013] Preferably, the screen material of the mobile five-layer vibrating screen is high manganese steel, the screen thickness is ≥8mm, the service life is ≥8000h, and the grading accuracy of steel slag particles during the screening process is ≥95%.

[0014] Preferably, in step (3), the permanent magnet drum magnetic separator, wet magnetic separator, and vertical ring high gradient magnetic separator meet the following requirements: the iron content of the processed product is ≤0.3%, and the metal recovery rate is ≥90%.

[0015] Preferably, the abrasion value of the road asphalt surface aggregate is ≤28%, the polishing value is ≥42, the water washing process adopts spray washing, the spray angle is 30°~60°, the water washing time is 10~15min, the dust removal rate of the steel slag surface after water washing is ≥98%, and the COD of the water washing wastewater is ≤50mg / L after treatment.

[0016] Preferably, the steel slag sand for rust removal has a Mohs hardness ≥6.5, a bulk density of 1.8~2.0g / cm³, a rust removal cleanliness grade ≥Sa2.5, a surface roughness of 16~23μm, and a mud content ≤0.3%. The mechanical hardness of the steel slag sand for rust removal is strengthened by a high-pressure roller pressing process, with a roller pressing pressure of 5~8MPa and a roller speed of 0.5~0.8m / s. After strengthening, the compressive strength of the steel slag sand is ≥150MPa, and the edge retention rate is ≥90%. The grading and screening of the steel slag sand for rust removal is carried out by a double-layer vibrating screen, with an upper screen mesh size of 8 mesh and a lower screen mesh size of 20 mesh. After screening, the particle size qualification rate of the steel slag sand is ≥99%.

[0017] Preferably, the Fe2O3 content of the cement iron correcting raw material is ≥35%, the SiO2 content is ≤13%, and the 80-mesh passing rate is ≥90%; the Pb, Cd, and Cr contents in the cement iron correcting raw material are ≤0.05%, ≤0.001%, and ≤0.01%, respectively; the ball milling process of the cement iron correcting raw material adopts an intermittent ball mill, the grinding media is high-chromium steel balls with a diameter of 20-40mm, the ball-to-material ratio is 4:1-6:1, and the specific surface area of ​​the steel slag powder after grinding is ≥350m² / kg.

[0018] Preferably, in step (1), the filter material of the high-temperature bag filter is selected from PTFE or basalt material with a temperature resistance of ≥320℃, and the dust collector shell is provided with a heat insulation layer with a thickness of ≥50mm; during the hot air conveying process, a heat insulation pipe with a heat insulation layer thickness of ≥50mm is used, and the temperature drop is ≤10℃, so as to ensure that the hot air temperature in the drying process is stable at 300~350℃.

[0019] Preferably, in step (1), the roller body of the roller crusher for liquid converter steel slag is provided with a cooling water channel. The cooling water flow rate of the cooling water channel is 10-15 m³ / h, and the inlet water temperature is ≤30℃. Through the synergistic effect of water cooling inside the roller body and contact cooling with steel slag, the roller tooth temperature is ensured to be ≤300℃, and the service life of the wear-resistant alloy material is extended to ≥5000h.

[0020] The beneficial effects of this invention are: (1) Significantly improved processing efficiency: The hot simmering cycle of liquid converter steel slag is shortened from 24 hours to 2 hours, and the overall processing time is about 3 hours, which is more than 85% more efficient than the traditional process; (2) Significantly enhanced product stability: The free CaO content in steel slag is ≤2.0%, which completely solves the hidden danger of hydration expansion and cracking, and the qualification rate of each product is ≥99%; (3) Outstanding environmental performance: The entire process is closed, achieving zero dust escape and centralized treatment of harmful gases. The wastewater recycling rate is ≥95%, reducing dust emissions by 80% and harmful gas emissions by 60% compared to traditional processes. The rod mill and ball mill processes are equipped with sound insulation and noise reduction facilities, and the noise is controlled below 85dB, meeting the noise emission standards for industrial enterprises. (4) Waste heat utilization and energy consumption optimization: The waste heat recovery process of liquid steel slag is innovatively adopted to form hot air, and the heat is accurately allocated as needed for drying of two types of materials, replacing external heat energy. The energy consumption of drying ton slag sand is reduced by more than 40%, realizing resource recycling. (5) High resource utilization rate and high added value: The utilization rate of all components of converter steel slag is ≥98%, achieving "zero stockpiling and full utilization"; the annual processing of 100,000 tons of converter steel slag can create direct economic benefits of 30-40 million yuan, and the added value is 30%-50% higher than that of traditional methods; (6) Significant social benefits: The utilization of each ton of converter steel slag can reduce the mining of natural stone by 1.0 to 1.2 tons, and the annual processing of 100,000 tons can reduce the land occupation by 1,000 to 1,500 square meters, which helps to achieve the "dual carbon" goal. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0023] See Figure 1 This invention discloses a method for efficient resource utilization of converter steel slag through grading, comprising the following steps: (1) Pretreatment of converter steel slag Liquid converter steel slag is sequentially subjected to roller crushing, pressurized hot curing, rod milling, and impurity removal processes to obtain pretreated steel slag. The roller crushing time is 20-30 minutes, and the crushed particle size is ≤300mm. Cold air is introduced for heat exchange during the crushing process. The hot air is converted into hot air for subsequent drying after being filtered by a high-temperature bag filter. The filter material of the high-temperature bag filter is made of PTFE or basalt material with a temperature resistance of ≥320℃. The shell of the dust collector is equipped with a heat insulation layer with a thickness of ≥50mm. During the hot air transportation process, heat-insulated pipes with a heat insulation layer thickness of ≥50mm are used, and the temperature drop is ≤10℃ to ensure that the hot air temperature in the drying process is stable at 300-350℃. The roller body of the roller crusher for liquid converter steel slag is equipped with a cooling water channel. The cooling water flow rate of the cooling water channel is 10-15 m³ / h, and the inlet water temperature is ≤30℃. Through the synergistic effect of water cooling inside the roller body and contact cooling with steel slag, the roller tooth temperature is ensured to be ≤300℃, and the service life of the wear-resistant alloy material is extended to ≥5000h.

[0024] The liquid steel slag solidifies after cooling at a temperature of 500-600℃. Pressurized hot curing is carried out in a sealed tank. After water is injected into the tank, a large amount of water vapor is generated using the residual heat of the steel slag to maintain the working pressure at 0.2-0.4MPa. The pressurized hot curing time is 1.5-2 hours, and the entire hot curing process is sealed. The air leakage rate of the sealed tank is ≤0.5%.

[0025] The rod mill is used to grind the slag to a particle size ≤63mm to remove the loose surface layer and large, unreacted particles. The media filling rate of the rod mill is 60%–70%. The impurity removal process uses a 63mm aperture drum screen combined with manual removal to remove refractory materials and scrap steel blocks with a diameter ≥63mm, ultimately obtaining pretreated steel slag with a purity ≥95% and free CaO ≤2.0%. (2) Grading and screening A mobile five-layer vibrating screen is used to classify the pretreated steel slag. The vibration frequency of the vibrating screen is 1200-1500 r / min, the amplitude is 5-8 mm, and the screen mesh size from top to bottom is 63 mm, 15 mm, 10 mm, 5 mm, and 8 mesh, which sequentially separates converter steel slag products of 16-63 mm, 10-15 mm, 5-10 mm, and <8 mesh. The screen material of the mobile five-layer vibrating screen is high manganese steel, the screen thickness is ≥8 mm, the service life is ≥8000 h, and the classification accuracy of steel slag particles during the screening process is ≥95%.

[0026] (3) Product adaptation treatment After iron removal, screening, grading, and compressive strength testing of the 16-63mm product using a permanent magnet drum magnetic separator, it is used as railway ballast. The magnetic field strength of the permanent magnet drum magnetic separator is 8000-10000Gs, and the 31.5-63mm product accounts for ≥95%. The 5-10mm and 10-15mm products, after iron removal by a wet magnetic separator, washing, drying, and gradation adjustment, are used as aggregates for road asphalt surface courses. The magnetic field strength of the wet magnetic separator is 10000-15000 Gs, the washing pressure is 0.3-0.5 MPa, and the drying uses hot air from crushing conversion at a temperature of 300-350℃. After gradation adjustment, the 5-10mm steel slag aggregate meets the following requirements: 100% passing rate on a 13.2mm square hole sieve, greater than 90% passing rate on a 9.5mm square hole sieve, less than 10% passing rate on a 4.75mm square hole sieve, and passing rate on a 2.36mm square hole sieve. The pass rate is less than 5%; the 10-15mm steel slag aggregate meets the following requirements: 100% pass rate for a 16mm square hole sieve, greater than 90% pass rate for a 13.2mm square hole sieve, less than 15% pass rate for a 9.5mm square hole sieve, and less than 5% pass rate for a 4.75mm square hole sieve; the abrasion value of the road asphalt surface aggregate is ≤28%, the polishing value is ≥42, the water washing process adopts spray washing, the spray angle is 30°~60°, the water washing time is 10~15min, the dust removal rate on the surface of the steel slag after water washing is ≥98%, and the COD of the water washing wastewater after treatment is ≤50mg / L.

[0027] Products with a mesh size <8 are crushed, converted, dried with hot air, and then subjected to mechanical hardening and grading screening to become steel slag sand for rust removal. The hot air temperature is 300-350℃, the drying time is 2-3 hours, and products with a mesh size <20 are screened out. The steel slag sand for rust removal has a Mohs hardness ≥6.5, a bulk density of 1.8-2.0 g / cm³, a rust removal cleanliness ≥Sa2.5, a surface roughness of 16-23 μm, and a mud content ≤0.3%. The mechanical hardening of the steel slag sand for rust removal is carried out using a high-pressure roller pressing process with a roller pressing pressure of 5-8 MPa and a roller speed of 0.5-0.8 m / s. After strengthening, the compressive strength of the steel slag sand is ≥150 MPa, and the edge retention rate is ≥90%. The grading screening of the steel slag sand for rust removal uses a double-layer vibrating screen with an upper screen mesh size of 8 mesh and a lower screen mesh size of 20 mesh. The qualified particle size of the steel slag sand after screening is ≥99%.

[0028] Products with a mesh size of <20 are ball-milled and subjected to iron removal by a vertical ring high-gradient magnetic separator, then pulverized to an 80-mesh size with a pass rate of ≥90%. These products are used as raw materials for iron correction in cement. The ball-milling time is 3–4 hours, and the magnetic field strength of the vertical ring high-gradient magnetic separator is 8000–10000 Gs. The permanent magnet drum magnetic separator, wet magnetic separator, and vertical ring high-gradient magnetic separator must meet the following requirements: the iron content of the processed product is ≤0.3%, and the metal recovery rate is ≥90%.

[0029] The Fe2O3 content of the cement iron correcting raw material is ≥35%, the SiO2 content is ≤13%, and the 80-mesh passing rate is ≥90%. The Pb, Cd, and Cr contents in the cement iron correcting raw material are ≤0.05%, ≤0.001%, and ≤0.01%, respectively. The ball milling process of the cement iron correcting raw material adopts an intermittent ball mill, the grinding media is high-chromium steel balls with a diameter of 20-40mm, the ball-to-material ratio is 4:1-6:1, and the specific surface area of ​​the steel slag powder after grinding is ≥350m² / kg.

[0030] (4) Wastewater and dust treatment and metal and waste heat recovery treatment Wastewater generated from washing is treated sequentially through sedimentation tanks, filters, and pH adjustment tanks before being recycled for the washing process. Dust generated during screening, crushing, and rod milling is collected by a high-temperature bag filter and then mixed into cement raw materials for reuse, achieving dust-free emissions. Metals recovered by magnetic separators in each process are returned to the steel plant for remelting. The conversion hot air generated during crushing is allocated according to the heat requirements of road asphalt surface aggregates and rust-removing steel slag sand, and used for the drying processes of these two types of materials respectively.

[0031] Example 1

[0032] Raw materials: 30t of liquid converter steel slag from a steel plant at a temperature of 1600℃, the main components of which include Fe2O3, CaO, SiO2, MgO, TiO2, etc. Preprocessing: Roller crushing: After processing for 25 minutes, the steel slag is cooled to 600-800℃, yielding 29.4t of particles ≤300mm (crushing rate 98%); the cooling water flow rate of the crushing device is 12m³ / h, the inlet water temperature is 28℃, and the roller tooth temperature is stabilized at 285℃; Pressurized hot curing: The residue was cured in a pressurized hot curing tank for 2 hours, maintaining a pressure of 0.3 MPa for the first 1.5 hours and 0.1 MPa for the next 0.5 hours; the SO2 emission concentration during the hot curing process was 8 mg / m³, and NO... X Emission concentration: 6 mg / m³; air leakage rate: 0.3%; Waste heat recovery: Cold air is introduced for heat exchange during the rolling crushing of liquid steel slag. After the hot air is filtered by a high-temperature bag filter (the filter material is PTFE, which can withstand temperatures up to 320°C), it is converted into hot air at 300°C and stored in a hot air buffer tank. Rod milling: The rod mill media filling rate is 65%, and grinding is carried out for 2 hours (processing capacity 15t / h), yielding 29t of particles ≤63mm. Impurity removal: 200 kg of impurities (mainly refractory material fragments and scrap steel particles) were removed by screening with a 63 mm aperture drum screen and manual removal, resulting in 28.8 t of pretreated steel slag (purity 95.3%, free CaO content 1.8%). Grading and screening: A moving five-layer vibrating screen (1500 r / min, amplitude 6 mm) was used for screening to obtain: 5.47 tons of converter steel slag (16-63mm) were produced, accounting for 19.0% of the total, of which 52% were particles (31.5-63mm). 6.31 tons of 10-15mm converter slag (accounting for 21.9%). 8.64 tons of 5-10mm converter slag (accounting for 30.0%). 5.18 tons of 8-20 mesh converter slag (accounting for 18.0%). <20 mesh converter slag 3.16t (accounting for 11.0%); Product processing: Railway ballast: 5.47t of steel slag was de-ironized using an 8000Gs permanent magnet drum separator (250kg of metal was recovered, with an iron content of 92%). After screening and grading, the following tests were conducted: Los Angeles abrasion rate of 26.5%, sodium sulfate solution immersion loss rate of 7.2%, and needle-like and flaky particle content of 6.8%, which meets the standard of TBT2140-2008. Road aggregate: 14.95t of steel slag (5-15mm). After iron removal by a 12000Gs wet magnetic separator, 0.4MPa spray washing (45° spray angle, 12min washing time), 300℃ waste heat hot air drying (1200m³ / h distribution air volume), and gradation adjustment, the following results were obtained: iron content 0.25%, moisture content 0.8%, abrasion value 26.8%, and polishing value 45, meeting the four relevant standards. The treated wastewater had a COD of 42mg / L and a suspended solids removal rate of 96%. Rust-removing steel slag sand: 5.18t of steel slag was dried with 300℃ waste heat hot air for 2.5h (distributed air volume 500m³ / h), then subjected to 8MPa high-pressure roller pressing (roller speed 0.6m / s), and screened through a double-layer vibrating screen (upper layer 8 mesh, lower layer 20 mesh) to obtain 4.83t of finished product (yield 93.2%, the main loss was ultrafine dust, which has been recovered to cement raw materials); testing: Mohs hardness 6.8, bulk density 1.92g / cm³, rust removal cleanliness Sa2.5 grade, mud content 0.2%, which meets the standard of GB / T17850.11-2011; Cement raw material: 3.16t of steel slag was ground in an intermittent ball mill for 3.5h (grinding media were 30mm diameter high-chromium steel balls, ball-to-material ratio 5:1), and then purified by magnetic separation in an 8000Gs vertical ring high gradient magnetic separator to obtain 2.97t of 80-mesh powder (pass rate 92%). Test results: Fe2O3 39.2%, SiO2 13%, Pb content 0.03%, Cd content 0.0008%, Cr content 0.008%, specific surface area 365m² / kg; This material replaced 35% of iron ore powder in cement production, resulting in a 28-day compressive strength of 38.6MPa. Benefits: The utilization rate of converter steel slag processed in this project was 99.33% (29.8t / 30t), with a total processing time of 3.0h; waste heat drying saved 0.8 tons of coal, equivalent to a power saving of 4651kWh; it generated direct economic benefits of RMB 12,050 (including RMB 7,500 in metal recovery revenue), with an average benefit of RMB 401.7 per ton; it reduced the mining of natural stone by 33 tons and CO2 emissions by 5.4 tons; dust emissions were 0.06 tons, a reduction of 80% compared to traditional processes; the noise level of the rod mill and ball mill processes was 82dB, which meets the noise emission standards for industrial enterprises.

[0033] Example 2 (Large-scale verification: 100,000 tons per year) Equipment configuration: 2 sets of roller crushing devices (processing capacity 50t / h), 4 pressurized hot blanching tanks (single tank volume 50m³), 3 rod mills, 2 sets of mobile five-layer vibrating screens, 4 sets of magnetic separation equipment (including permanent magnet drum type, wet type, and vertical ring high gradient type), 2 sets of high temperature bag dust collectors, 1 set of hot air buffer tank (volume 100m³) and supporting wastewater treatment system; Key parameters: Roller crushing time 28 min, pressurized hot quenching pressure 0.35 MPa, cycle 2.2 h, moving screen vibration frequency 1400 r / min, hot air temperature 300℃±5℃, water resource utilization rate 96%, metal recovery rate 98.5%; Product output: 18,000 tons of 16-63mm railway ballast, 22,000 tons of 10-15mm road aggregate, 28,000 tons of 5-10mm road aggregate, 17,000 tons of 8-20 mesh rust-removing steel slag sand, and 15,000 tons of <20 mesh cement raw materials; Benefits: It generates direct economic benefits of 40.2 million yuan per year, increases the added value per ton by 402 yuan; saves 2,667 tons of standard coal, reduces the mining of natural stone by 110,000 tons, reduces land occupation by 1,200 square meters, reduces CO2 emissions by 18,000 tons, and reduces dust emissions by more than 80%.

[0034] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for efficient resource utilization of converter steel slag through classification, characterized in that, Includes the following steps: (1) Pretreatment of converter steel slag Liquid converter slag is sequentially subjected to roller crushing, pressurized hot curing, rod milling, and impurity removal processes to obtain pretreated slag. The roller crushing time is 20-30 minutes, and the crushed particle size is ≤300mm. During the crushing process, cold air is introduced for heat exchange. The hot air is converted into hot air for subsequent drying after dust removal by a high-temperature bag filter. The liquid slag is cooled and solidified at a temperature of 500-600℃. Pressurized hot curing is carried out in a sealed tank. Water is injected into the tank, and a large amount of water vapor is generated using the residual heat of the slag. The working pressure is maintained at 0.2-0.4MPa for at least 1 hour. The rod milling is performed to a particle size of ≤63mm to remove the loose surface layer and large particles that have not been fully reacted. The impurity removal process uses a 63mm aperture drum screen combined with manual removal to remove refractory materials and scrap steel blocks with a diameter ≥63mm. Finally, pretreated slag with a purity ≥95% and free CaO ≤2.0% is obtained. (2) Grading and screening A mobile five-layer vibrating screen was used to classify the pretreated steel slag. The vibration frequency of the vibrating screen was 1200-1500 r / min, the amplitude was 5-8 mm, and the screen mesh size from top to bottom was 63 mm, 15 mm, 10 mm, 5 mm, and 8 mesh, which separated converter steel slag products of 16-63 mm, 10-15 mm, 5-10 mm, and <8 mesh in sequence. (3) Product adaptation treatment After iron removal, screening, grading, and compressive strength testing of the 16-63mm product using a permanent magnet drum magnetic separator, it is used as railway ballast. The magnetic field strength of the permanent magnet drum magnetic separator is 8000-10000Gs, and the 31.5-63mm product accounts for ≥95%. The 5-10mm and 10-15mm steel slag aggregates, after being treated with a wet magnetic separator for iron removal, washing, drying, and gradation adjustment, are used as aggregates for road asphalt surface courses. The magnetic field strength of the wet magnetic separator is 10000-15000 Gs, the washing pressure is 0.3-0.5 MPa, and the drying process uses hot air from a crushing process at a temperature of 300-350℃. After gradation adjustment, the 5-10mm steel slag aggregate meets the following requirements: 100% passing rate on a 13.2mm square hole sieve, greater than 90% passing rate on a 9.5mm square hole sieve, less than 10% passing rate on a 4.75mm square hole sieve, and less than 5% passing rate on a 2.36mm square hole sieve; the 10-15mm steel slag aggregate meets the following requirements: 100% passing rate on a 16mm square hole sieve, greater than 90% passing rate on a 13.2mm square hole sieve, less than 15% passing rate on a 9.5mm square hole sieve, and less than 5% passing rate on a 4.75mm square hole sieve. The product with a mesh size <8 is dried by hot air after crushing and conversion, and then mechanically hardened and graded. It is then used as steel slag sand for rust removal. The hot air temperature is 300-350℃ and the drying time is 2-3 hours. The product with a mesh size <20 is then screened out. The product with a mesh size of <20 mesh is ball-milled and then subjected to iron removal by a vertical ring high gradient magnetic separator. It is then pulverized to a mesh size of ≥90% and used as a raw material for correcting iron content in cement. The ball milling time is 3-4 hours and the magnetic field strength of the vertical ring high gradient magnetic separator is 8000-10000 Gs. (4) Wastewater and dust treatment and metal and waste heat recovery treatment Wastewater generated from washing is treated sequentially through sedimentation tanks, filters, and pH adjustment tanks before being recycled for the washing process. Dust generated during screening, crushing, and rod milling is collected by a high-temperature bag filter and then mixed into cement raw materials for reuse, achieving dust-free emissions. Metals recovered by magnetic separators in each process are returned to the steel plant for remelting. The conversion hot air generated during crushing is allocated according to the heat requirements of road asphalt surface aggregates and rust-removing steel slag sand, and used for the drying processes of these two types of materials respectively.

2. The method according to claim 1, characterized in that, In step (1), the pressurized hot simmering time is 1.5 to 2 hours, and the hot simmering process is completely sealed, with the air leakage rate of the sealed tank ≤0.5%.

3. The method according to claim 1, characterized in that, In step (1), the media filling rate of the rod mill used in the rod mill is 60% to 70%.

4. The method according to claim 1, characterized in that, The mobile five-layer vibrating screen is made of high manganese steel, with a screen thickness of ≥8mm, a service life of ≥8000h, and a grading accuracy of steel slag particles of ≥95% during the screening process.

5. The method according to claim 1, characterized in that, In step (3), the permanent magnet drum magnetic separator, wet magnetic separator, and vertical ring high gradient magnetic separator meet the following requirements: the iron content of the processed product is ≤0.3%, and the metal recovery rate is ≥90%.

6. The method according to claim 1, characterized in that, The abrasion value of the aggregate in the asphalt pavement of the road is ≤28%, the polishing value is ≥42, the water washing process adopts spray washing, the spray angle is 30°~60°, the water washing time is 10~15min, the dust removal rate on the surface of steel slag after water washing is ≥98%, and the COD of the water washing wastewater is ≤50mg / L after treatment.

7. The method according to claim 1, characterized in that, The steel slag sand used for rust removal has a Mohs hardness ≥6.5, a bulk density of 1.8~2.0g / cm³, a rust removal cleanliness grade ≥Sa2.5, a surface roughness of 16~23μm, and a mud content ≤0.3%. The mechanical hardness of the steel slag sand used for rust removal is strengthened by a high-pressure roller pressing process, with a roller pressing pressure of 5~8MPa and a roller speed of 0.5~0.8m / s. After strengthening, the compressive strength of the steel slag sand is ≥150MPa, and the edge retention rate is ≥90%. The grading and screening of the steel slag sand used for rust removal is carried out by a double-layer vibrating screen, with an upper screen mesh size of 8 mesh and a lower screen mesh size of 20 mesh. After screening, the particle size qualification rate of the steel slag sand is ≥99%.

8. The method according to claim 1, characterized in that, The Fe2O3 content of the cement iron correcting raw material is ≥35%, the SiO2 content is ≤13%, and the 80-mesh passing rate is ≥90%. The Pb, Cd, and Cr contents in the cement iron correcting raw material are ≤0.05%, ≤0.001%, and ≤0.01%, respectively. The ball milling process of the cement iron correcting raw material adopts an intermittent ball mill, the grinding media is high-chromium steel balls with a diameter of 20-40mm, the ball-to-material ratio is 4:1-6:1, and the specific surface area of ​​the steel slag powder after grinding is ≥350m² / kg.

9. The method according to claim 1, characterized in that, In step (1), the filter material of the high-temperature bag filter is selected from PTFE or basalt material with a temperature resistance of ≥320℃, and the dust collector shell is equipped with a heat insulation layer with a thickness of ≥50mm; during the hot air conveying process, heat insulation pipes with a heat insulation layer thickness of ≥50mm are used, and the temperature drop is ≤10℃, so as to ensure that the hot air temperature in the drying process is stable at 300~350℃.

10. The method according to claim 1, characterized in that, In step (1), the roller body of the roller crusher for liquid converter steel slag is equipped with a cooling water channel. The cooling water flow rate of the cooling water channel is 10-15 m³ / h, and the inlet water temperature is ≤30℃. Through the synergistic effect of water cooling inside the roller body and contact cooling of steel slag, the roller tooth temperature is ensured to be ≤300℃, and the service life of wear-resistant alloy material is extended to ≥5000h.

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