A method for disposing steel slag using an ironmaking system

Abstract

The application discloses a method for disposing steel slag by using an iron-making system, and comprises the following steps: S1, placing the steel slag above a tapping channel of a blast furnace, and preheating the steel slag by using waste heat; and S2, after 20-30 minutes of tapping slag from the blast furnace, the preheated steel slag is evenly added into liquid slag iron generated in a tapping slag iron process, and a molten mixed slag is formed in a main iron channel section; in the step S2, the steel slag adding position is located in the main iron channel section at a distance of 2-4 m from a tapping hole of the blast furnace. The method for disposing the steel slag by using the iron-making system can solve the problems of low stability and low cementing activity of the steel slag, does not increase a new process, is simple in process, low in cost, and opens up a new way for resource utilization of the steel slag.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of steel slag treatment, and in particular, the present application relates to a method for disposing steel slag by using an ironmaking system. BACKGROUND

[0002] Steel slag is the main solid waste (referred to as solid waste) generated in the steelmaking process of the steel industry, and its production amount is 10%-15% of the crude steel output. Steel slag contains a large amount of valuable components such as calcium, magnesium, and iron, and is a valuable solid waste resource. However, due to the poor stability of steel slag, the resource utilization rate of steel slag is less than 25% at present, and a large amount of steel slag accumulation not only occupies a large amount of land, but also causes environmental pollution and resource waste. As a typical metallurgical bulk solid waste, efficient resource utilization of steel slag has always been an urgent demand of the steel industry. After decades of development, the current steel slag treatment processes and technologies at home and abroad mainly include hot splashing method, hot stewing method, shallow tray method, water quenching method, air quenching method, and roller method, etc., but these treatment methods can only partially decompose the free calcium oxide in steel slag. At the same time, the steel slag treated by the above processes is mainly used for building materials, road construction, microcrystalline glass, agricultural fertilizer, etc., among which the application in the building material field, especially the preparation of Portland cement by using the cementitious properties of steel slag, has become the mainstream way to realize its large-scale resource utilization, and the utilization amount accounts for 30%-50% of the total amount of steel slag disposal. However, on June 1, 2024, the "General Portland Cement" (GB175-2023) began to be formally implemented, and steel slag can no longer be used as a mixed material for general Portland cement. Therefore, how to realize the large-scale resource utilization of steel slag has become a common problem that the steel industry urgently needs to solve.

[0003] The volume expansion caused by the hydration reaction of free calcium oxide (f-CaO) in steel slag is the main reason for its poor stability, and therefore how to reduce the content of free calcium oxide in steel slag is a key problem for the resource utilization of steel slag. It has been found that materials rich in acidic oxides such as silicon and aluminum can effectively capture free calcium oxide in steel slag and convert it into silicates or aluminosilicates with good stability. The blast furnace smelting process is to reduce iron ore to liquid metal iron and molten slag at high temperature, and the liquid slag iron carrying a large amount of sensible heat is separated due to the difference in specific gravity when passing through the main iron channel and slag channel in front of the furnace. The separated liquid iron enters the steelmaking process, and the molten slag generally enters the slag treatment system to obtain water slag, which contains a lot of SiO2 and Al2O3, and is a typical silicate material for cement production (the utilization rate is more than 80% at present), so it can be used as a capturing agent to capture free calcium oxide in steel slag.

[0004] A method for modifying steel slag into blast furnace slag is disclosed in Chinese patent CN101367625. Dry steel slag is added to the slag channel at a distance of 0-5 m from the main iron channel of the blast furnace. Under high temperature conditions, the basic oxides in the steel slag react with the acidic oxides in the blast furnace slag to form silicates. After water quenching treatment, water slag is obtained for cement production. However, the added steel slag is on the surface of the blast furnace slag. Except for the contact surface, the steel slag is difficult to fully contact and react with the blast furnace slag. At the same time, due to the fact that the temperature of the slag in the slag channel has been significantly reduced and the heat capacity of the slag is limited, the reaction rate of free calcium oxide and acidic substances is affected, ultimately reducing the digestion efficiency and steel slag treatment capacity.

[0005] Chinese patent CN106517834 discloses a method for harmless treatment of stainless steel slag at high temperature using molten blast furnace slag. First, the molten slag discharged from blast furnace ironmaking is placed in an electrically heated slag pot to maintain its molten state. Then, stainless steel slag is added to the molten blast furnace slag to form a mixed slag. After water quenching, glassy structure-based slag is obtained, and heavy metal Cr is fixed in the glassy slag. This method requires heat supplement for the slag pot, thus requiring new equipment and additional energy consumption.

[0006] Chinese patent CN112853010 discloses a method for green treatment of electric furnace stainless steel slag. Molten steel slag is loaded into a slag pot and kept in a molten state by insulation. Then, molten blast furnace slag is poured into the slag pot, and the steel slag and blast furnace slag are uniformly mixed by stirring. After a period of time, the mixed slag is slowly cooled and then treated by hot stewing to obtain tail slag. This method requires a long treatment time to ensure that Cr is completely solidified in the slag, and the slag pot needs to be heated and insulated, which increases the process and consumes additional energy.

[0007] Chinese patent CN102559960 discloses a steel slag treatment method. Hot converter steel slag and blast furnace slag are mixed in an electric arc furnace at a certain ratio. The basic oxides and acidic oxides in the molten slag are allowed to fully react at a certain temperature, and then glassy solid slag is formed after rapid cooling. However, during the process of melting and mixing steel slag and blast furnace slag in the electric arc furnace, the iron oxides in the steel slag are reduced to metallic iron by graphite carbon, causing the molten slag to dry out, thus prolonging the digestion time and reducing the digestion efficiency. The energy consumption of the electric arc furnace is also increased.

[0008] Chinese patent CN102492792 discloses a method for modifying and treating molten steel slag. Converter steel slag at 1500-1700℃, blast furnace slag at 1400-1550℃, and lime powder are modified and treated in an insulated slag pot. This method can improve the cementitious activity of steel slag, but the addition of lime powder during the modification process may pose new volume stability problems for the modified slag. In addition, the slag pot needs to be insulated for a long time, increasing energy consumption.

[0009] Chinese patent publication CN106045347 discloses a method for melting and digesting free calcium oxide in converter steel slag. First, the steel slag with a temperature above 1450℃ is loaded into a slag discharge tank, then the blast furnace slag with a temperature above 1400℃ and the silicon-containing waste are added into the slag discharge tank, the free calcium oxide in the steel slag is digested by the acid substance in the blast furnace slag and the SiO2 in the silicon-containing waste, and finally the modified steel slag is cooled by air cooling or water cooling. The digestion process in the method is carried out in the slag discharge tank without heat supplement, and the addition of cold silicon-containing waste and the heat loss will inevitably reduce the temperature of the slag, thereby affecting the reaction rate between the basic oxide and the acid oxide, and further affecting the digestion efficiency. At the same time, the digestion process needs a certain time, thereby affecting the connection between processes.

[0010] It is desirable to provide an improved method for disposing steel slag by using an ironmaking system, in particular a method for digesting free calcium oxide in the steel slag and improving the cementitious activity of the steel slag, so as to realize efficient resource utilization of the steel slag. SUMMARY

[0011] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a method for disposing steel slag by using an ironmaking system, which aims to digest free calcium oxide in the steel slag and improve the cementitious activity of the steel slag.

[0012] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows: a method for disposing steel slag by using an ironmaking system, comprising the steps of:

[0013] S1, placing the steel slag above the taphole of a blast furnace, and preheating the steel slag by using the residual heat;

[0014] S2, after 20-30 minutes of the slag tapping process of the blast furnace, uniformly adding the preheated steel slag into the liquid slag iron generated in the slag tapping process of the blast furnace, to form a molten mixed slag in the main iron channel section.

[0015] In step S2, the position of adding the steel slag is located in the main iron channel section at a distance of 2-4 m from the taphole of the blast furnace.

[0016] The particle size of the steel slag is controlled to be below 5 mm.

[0017] In step S2, the mass of the added steel slag is not more than 50% of the mass of the liquid slag iron generated in the slag tapping process of the blast furnace at one time.

[0018] In step S2, the adding speed of the steel slag is wherein, δ is a speed coefficient, taken as 1.20-1.40, Q is the mass of the liquid slag iron tapped from the blast furnace per unit time, k is the ratio of the weight of the added steel slag to the weight of the liquid slag generated in the slag tapping process of the blast furnace at one time, and μ is the slag ratio, i.e. the mass of the molten slag generated per ton of molten iron.

[0019] Mass of liquid slag iron discharged from the blast furnace per unit time Wherein, d is the average diameter of the taphole; g represents the gravity acceleration constant; h is the liquid level difference of the taphole outlet center line; l represents the taphole depth; P is the blast furnace internal pressure; λ represents the friction coefficient of the taphole wall; and ρ is the average density of the liquid slag iron.

[0020] The method for disposing steel slag by using an iron-making system has the following beneficial effects:

[0021] (1) The steel slag is continuously and uniformly added in the main iron channel of the blast furnace, at which time the liquid slag iron has a high temperature, the sensible heat of the liquid molten slag iron can be fully utilized, the steel slag can fully react with the molten slag iron, the free calcium oxide in the steel slag can be fully digested, and the cementitious activity of the steel slag can be improved.

[0022] (2) The steel slag is added in the process of discharging slag iron from the blast furnace, at which time the liquid slag iron is in a turbulent fluid state, the kinetic condition is good, the steel slag can fully contact with the liquid slag iron, and thus the reaction speed and the reaction degree between the steel slag and the blast furnace slag iron are improved.

[0023] (3) The steel slag treated by the method can be the original slag after the existing steel slag primary treatment process, or the tail slag after iron selection, and has stronger applicability. Meanwhile, the steel slag particle size is controlled below 5 mm, which can be steel slag particles or steel slag powder, so that the steel slag can fully react with the high-temperature molten slag iron and the digestion efficiency is improved.

[0024] (4) The method does not increase a new process, has simple process, no pollution in the treatment process, low cost, and remarkable economic and social benefits, and has important practical significance for promoting the resource utilization of the steel slag. BRIEF DESCRIPTION OF DRAWINGS

[0025] The present specification includes the following drawings, and the shown contents are as follows:

[0026] Figure 1 is a process flow diagram of the method for cooperatively disposing steel slag by using the process of discharging slag iron from the blast furnace. DETAILED DESCRIPTION

[0027] The specific embodiments of the present application are further described in detail below with reference to the drawings and by describing the embodiments, the purpose is to help the technicians in the field to have more complete, accurate and in-depth understanding of the concept and technical solution of the present application, and to help the implementation.

[0028] As shown in Figure 1 , the present application provides a method for cooperatively disposing steel slag by using the process of discharging slag iron from the blast furnace, which comprises the following steps:

[0029] S1, the steel slag is placed above the furnace runner, and the steel slag is preheated by using the waste heat;

[0030] S2, after the furnace slag iron is discharged for 20-30 minutes, the preheated steel slag is uniformly added into the liquid slag iron generated in the furnace slag iron process, and a molten mixed slag is formed in the main runner section;

[0031] S3, the molten mixed slag is treated by the water quenching treatment system;

[0032] S4, the water quenched slag is obtained after cooling.

[0033] Specifically, the present application is directed to the problems of slow digestion speed of free calcium oxide, limited steel slag treatment capacity, new process and energy consumption in the process of steel slag modification and resource utilization, and a method for disposing steel slag by using the ironmaking system is proposed. The steel slag is directly and uniformly added into the molten slag iron in the main runner of the blast furnace, and the steel slag and the liquid slag iron fully react in the turbulent process of the high-temperature slag iron. Since the liquid slag iron has high temperature and is in a turbulent state, the digestion speed of free calcium oxide and other alkaline oxides can be greatly improved, and the steel slag treatment capacity can be increased. This method does not increase new processes and energy consumption, has simple process, no pollution in the treatment process and low cost.

[0034] The working principle of the method is as follows: the steel slag is directly added into the liquid slag iron in the main runner section of the blast furnace, and the steel slag and the liquid slag iron fully react in the turbulent process of the high-temperature liquid slag iron. The iron oxides in the steel slag can be reduced by the dissolved carbon in the molten iron and enter the molten iron, and the alkaline oxides such as free calcium oxide react with the acidic oxides in the blast furnace slag to form silicates. The molten mixed slag formed after the reaction enters the water quenching treatment system through the slag runner, and finally the water quenched slag is obtained, which can be used for cement production.

[0035] In the above step S2, the steel slag is directly added into the main runner section, which is used for separating slag iron and guiding molten iron in the process of discharging slag iron from the blast furnace. The liquid slag iron discharged from the blast furnace enters from the inlet of the main runner section, and the liquid slag iron and the steel slag are mixed and fully reacted, and then the slag flows to the slag runner through the skimmer.

[0036] As a preferred, the particle size of the steel slag is controlled below 5mm.

[0037] In the above step S2, the steel slag is continuously and uniformly added into the main runner section, and the steel slag addition position is located in the main runner section 2-4m away from the blast furnace tap hole along the flow direction of the liquid slag iron in the main runner section. Exemplarily, the distance between the steel slag addition position and the blast furnace tap hole along the flow direction of the liquid slag iron in the main runner section can be set to 2.0m, 2.5m, 3.0m, 3.5m or 4.0m.

[0038] In the above step S2, the steel slag is continuously and uniformly added, and the mass of the added steel slag is not more than 50% of the mass of the liquid slag iron generated in one time of the blast furnace slag tapping process (i.e. the ratio of the weight of the added steel slag to the weight of the liquid slag generated in one time of the blast furnace slag tapping process is represented by k).

[0039] In the above step S2, the steel slag is continuously and uniformly added, and the speed (v: the mass of the added steel slag per unit time) of the added steel slag is related to the mass Q of the tapped slag iron per unit time, the slag ratio μ (i.e. the mass of the molten slag generated per ton of the produced liquid iron), and the mass ratio k of the added steel slag, and is specifically calculated as follows:

[0040]

[0041] In the formula, δ is a speed coefficient, and is 1.20-1.40; k is the ratio of the weight of the added steel slag to the weight of the liquid slag generated in one time of the blast furnace slag tapping process, μ is the slag ratio (i.e. the mass of the molten slag generated per ton of the produced liquid iron); and Q represents the speed of the tapped liquid slag iron of the blast furnace, i.e. the mass of the tapped liquid slag iron per unit time, and can be calculated by formula (2).

[0042]

[0043] In the formula, d is the average diameter of the blast furnace tuyere; g represents the acceleration constant of gravity; h is the liquid level difference of the center line of the blast furnace tuyere outlet; I represents the blast furnace tuyere depth; P is the blast furnace internal pressure; λ represents the friction coefficient of the blast furnace tuyere wall; and p is the average density of the liquid slag iron.

[0044] A blast furnace with a volume of 3200m 3 was taken as the object (slag ratio μ = 360 kg / t, and tapped slag iron speed Q = 11.56 t / min), and the blast furnace slag and the converter hot holding steel slag generated in the smelting process were selected as the raw materials. The chemical composition of the blast furnace slag is shown in Table 1, and the chemical composition of the converter steel slag is shown in Table 2.

[0045] Table 1 Chemical composition of blast furnace slag (%)

[0046] CaO SiO2 MgO Al2O3 FeO MnO TiO2 S 37.77 31.66 6.99 15.25 0.54 0.458 0.854 0.933

[0047] Table 2 Chemical composition of converter steel slag (%)

[0048] CaO SiO2 MgO Al2O3 Fe2O3 FeO MnO P2O5 f-CaO 39.73 17.34 8.84 2.47 14.16 12.53 1.76 1.23 1.48

[0049] Example 1:

[0050] In this embodiment, during the process of slagging iron in blast furnace ironmaking, the preheated steel slag is added to the liquid slag iron in the main iron channel area 4 m away from the blast furnace iron notch, the mass of converter steel slag is 10% of the mass of liquid slag produced in the blast furnace slagging iron process, the steel slag adding speed is 0.43 t / min, and the above-mentioned steel slag is pre-ironing steel slag, and the particle size of the steel slag is less than 5 mm. After the blast furnace main iron channel section, slag channel section and water quenching treatment, water quenched slag is obtained. Through detection and analysis, the content of free calcium oxide in the water quenched slag is 0.32%, and the glass content is 93.48%.

[0051] The activity and mortar cube strength of the above water quenched slag powder are detected according to the national standard (GB / T 18046-2017 and GB / T 17671-2021) method, and the results are shown in Table 3. The 7-day activity index of the water quenched slag powder is 88.43%, the 28-day activity index is 98.76%, the 7-day compressive strength of the mortar cube is 30.62 MPa, and the 28-day compressive strength is 55.78 MPa, which meets the requirements of S95 slag powder and meets the requirements of building cement materials.

[0052] Example 2:

[0053] In this embodiment, during the process of slagging iron in blast furnace ironmaking, the preheated steel slag is added to the liquid slag iron in the main iron channel area 3.5 m away from the blast furnace iron notch, the mass of converter steel slag is 20% of the mass of liquid slag produced in the blast furnace slagging iron process, the steel slag adding speed is 0.83 t / min, and the above-mentioned steel slag is pre-ironing steel slag, and the particle size of the steel slag is less than 4 mm. After the blast furnace main iron channel section, slag channel section and water quenching treatment, water quenched slag is obtained. Through detection and analysis, the content of free calcium oxide in the water quenched slag is 0.45%, and the glass content is 91.26%.

[0054] The activity and mortar cube strength of the above water quenched slag powder are detected according to the national standard (GB / T 18046-2017 and GB / T 17671-2021) method, and the results are shown in Table 3. The 7-day activity index of the water quenched slag powder is 88.43%, the 28-day activity index is 98.76%, the 7-day compressive strength of the mortar cube is 30.62 MPa, and the 28-day compressive strength is 55.78 MPa, which meets the requirements of S95 slag powder and meets the requirements of building cement materials.

[0055] Example 3:

[0056] In this embodiment, during the process of slagging iron in blast furnace ironmaking, the preheated steel slag is added to the liquid slag iron in the main iron channel area 3 m away from the blast furnace iron notch, the mass of converter steel slag is 30% of the mass of liquid slag produced in the blast furnace slagging iron process, the steel slag adding speed is 1.19 t / min, and the above used steel slag is the steel slag before iron selection, the particle size of steel slag is less than 3 mm. After the blast furnace main iron channel section, slag channel section and water quenching treatment, water quenched slag is obtained. Through detection and analysis, the content of free calcium oxide in the water quenched slag is 0.51%, and the glass content is 90.42%.

[0057] In this embodiment, the activity and mortar cube strength of the above water quenched slag powder are detected according to the national standard (GB / T 18046-2017 and GB / T 17671-2021) method, and the results are shown in Table 3. The 7-day activity index of the water quenched slag powder is 83.26%, the 28-day activity index is 96.21%, the 7-day compressive strength of the mortar cube is 28.83 MPa, and the 28-day compressive strength is 54.34 MPa, which meets the requirements of S95 slag powder and meets the requirements of building cement materials.

[0058] Example 4:

[0059] In this embodiment, during the process of slagging iron in blast furnace ironmaking, the preheated steel slag is added to the liquid slag iron in the main iron channel area 2.5 m away from the blast furnace iron notch, the mass of converter steel slag is 40% of the mass of liquid slag produced in the blast furnace slagging iron process, the steel slag adding speed is 1.53 t / min, and the above used steel slag is the steel slag after iron selection in Table 2, the particle size of steel slag is less than 2 mm. After the blast furnace main iron channel section, slag channel section and water quenching treatment, water quenched slag is obtained. Through detection and analysis, the content of free calcium oxide in the water quenched slag is 0.48%, and the glass content is 91.33%.

[0060] The activity and mortar cube strength of the above water quenched slag powder are detected according to the national standard (GB / T 18046-2017 and GB / T 17671-2021) method, and the results are shown in Table 3. The 7-day activity index of the water quenched slag powder is 84.12%, the 28-day activity index is 97.07%, the 7-day compressive strength of the mortar cube is 29.13 MPa, and the 28-day compressive strength is 54.83 MPa, which meets the requirements of S95 slag powder and meets the requirements of building cement materials.

[0061] Example 5:

[0062] In the present embodiment, in the process of tapping slag iron from a blast furnace, the preheated steel slag is added to the liquid slag iron at a main iron channel area 2 m away from the blast furnace tapping hole, the mass of the converter steel slag added is 50% of the mass of the liquid slag produced in the blast furnace slag tapping process, the steel slag addition speed is 1.84 t / min, and the steel slag used above is the steel slag after iron removal in Table 2, the particle size of the steel slag is less than 3 mm. After the blast furnace main iron channel section, slag channel section and water quenching treatment, water quenched slag is obtained. Through detection and analysis, the content of free calcium oxide in the water quenched slag is 0.59%, and the glass content is 89.68%.

[0063] The activity and mortar cube strength of the above water quenched slag powder are detected according to the national standard (GB / T 18046-2017 and GB / T 17671-2021) method, and the results are shown in Table 3. The 7-day activity index of the water quenched slag powder is 79.67%, the 28-day activity index is 95.94%, the 7-day compressive strength of the mortar cube is 27.59 MPa, and the 28-day compressive strength is 54.19 MPa, which meets the requirements of S95 slag powder and meets the requirements of building cement materials.

[0064] Table 3 Activity index and mortar cube strength of water quenched slag powder in the embodiment

[0065]

[0066] The present application is described above with reference to the drawings. Obviously, the specific implementation of the present application is not limited by the above manner. As long as various non-essential improvements are made by using the method concept and technical scheme of the present application; or without improvement, the above concept and technical scheme of the present application are directly applied to other occasions, which are within the protection scope of the present application.

Claims

1. A method for disposing steel slag using an ironmaking system, characterized by, The method comprises the steps of: S1, placing the steel slag above the taphole of a blast furnace to preheat the steel slag by using waste heat; S2, after 20-30 minutes of the slag tapping of the blast furnace, the preheated steel slag is evenly added into the liquid slag iron produced in the slag tapping process of the blast furnace to form a molten mixed slag in the main iron channel section; In the step S2, the adding position of the steel slag is located in the main iron channel section at a distance of 2-4 m from the taphole of the blast furnace; The speed of adding the steel slag in step S2 wherein, δ is a speed coefficient, taken as 1.20-1.40, Q is the mass of liquid slag iron discharged from the blast furnace per unit time, k is the ratio of the weight of the added steel slag to the weight of the liquid slag produced in the process of discharging the iron from the blast furnace, μ is the slag ratio, i.e. the mass of molten slag produced per ton of molten iron; mass of liquid slag discharged from the blast furnace per unit time wherein, d is the average diameter of the tap hole; g denotes the constant of gravitational acceleration; h is the difference in liquid level of the center line of the tap hole outlet; l denotes the depth of the tap hole; P is the pressure in the blast furnace; λ denotes the friction coefficient of the tap hole wall; ρ is the average density of the liquid slag.

2. The method for disposing steel slag using an ironmaking system according to claim 1, characterized by, The particle size of the steel slag is controlled to be below 5 mm.

3. The method for disposing steel slag using an iron-making system according to claim 1, characterized by, In the step S2, the mass of the added steel slag is not more than 50% of the mass of the liquid molten blast furnace slag produced in the slag tapping process of the blast furnace at one time.

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