Method for treating steel slag by utilizing ironmaking system

Abstract

The invention discloses a method for treating steel slag by utilizing an ironmaking system, which comprises the following steps: S1, placing the steel slag above a blast furnace tapping channel, and preheating the steel slag by utilizing waste heat; s2, 20-30 minutes after the slag iron is discharged from the blast furnace, the preheated steel slag is uniformly added into liquid slag iron generated in the process of discharging the slag iron from the blast furnace, and molten mixed slag is formed in the main iron runner section; in the step S2, the steel slag adding position is located in a main iron runner section 2-4 m away from a blast furnace taphole. The method for treating the steel slag by using the ironmaking system can simultaneously solve the problems of low stability and low gelation activity of the steel slag, does not add new procedures, is simple in process and low in cost, and opens up a new way for resource utilization of the steel slag.

Description

Technical Field

[0001] The invention belongs to the technical field of steel slag treatment, and in particular, relates to a method for treating steel slag using an ironmaking system. Background Art

[0002] Steel slag is the main solid waste (referred to as solid waste) generated during the steelmaking production process of the steel industry, and its production volume accounts for 10%-15% of 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 current resource utilization rate of steel slag is less than 25%. The accumulation of a large amount of steel slag not only occupies a large amount of land, but also causes environmental pollution and waste of resources. As a typical metallurgical bulk solid waste, efficient resource utilization of steel slag has always been an urgent need faced by the steel industry. After decades of development, the current steel slag treatment processes and technologies at home and abroad mainly include hot pouring, hot stewing, shallow plate method, water quenching, wind quenching and drum method, but these treatment methods can only partially eliminate the free calcium oxide in steel slag. At the same time, steel slag treated by the above process is mainly used in building materials, road construction, microcrystalline glass, agricultural fertilizers, etc. Among them, it is used in the field of building materials, especially the use of steel slag gelling properties to prepare silicate cement, which has become the mainstream way to achieve its large-scale resource utilization, and its utilization accounts for 30%-50% of the current total steel slag disposal. However, on June 1, 2024, "General Portland Cement" (GB175-2023) will be officially implemented, and steel slag will no longer be used as a mixed material for general Portland cement. Therefore, how to achieve 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. Therefore, how to reduce the content of free calcium oxide in steel slag is a key issue in the resource utilization of steel slag. Studies have 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 into liquid metallic iron and molten slag at high temperature. The liquid slag iron carrying a large amount of sensible heat is separated due to different specific gravities when passing through the main iron ditch and slag ditch 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 more SiO2 and Al2O3. It is a typical silicate material that can be used for cement production (the current utilization rate is more than 80%), so it can be used as a digester to capture free calcium oxide in steel slag.

[0004] Chinese patent with publication number CN101367625 discloses a method for reforming steel slag into blast furnace slag, wherein dry steel slag is added to a slag ditch 0-5m away from the main iron ditch of the blast furnace, and the alkaline oxides in the steel slag react with the acidic oxides in the blast furnace slag under high temperature conditions to form silicates, and the slag is obtained after water quenching for cement production. However, the added steel slag is on the surface of the blast furnace slag, and it is difficult for the steel slag to fully contact and react with the blast furnace slag except for the contact surface between the two. At the same time, since the slag temperature in the slag ditch has been significantly reduced and the slag heat capacity is limited, the reaction rate of free calcium oxide and acidic substances is affected, and finally the digestion efficiency and the amount of steel slag treated are reduced.

[0005] The Chinese patent with publication number CN106517834 discloses a method for high-temperature harmless treatment of stainless steel slag using molten blast furnace slag. First, the molten slag discharged from the blast furnace ironmaking is placed in an electrically heated slag pot to keep it in a molten state, and then the stainless steel slag is added to the molten blast furnace slag to form a mixed slag. After water quenching, a slag with a glassy structure is obtained, and the heavy metal Cr is fixed in the glassy slag. This method requires supplementary heating of the slag pot, which requires new equipment and consumes additional energy.

[0006] The Chinese patent with publication number CN112853010 discloses a green method for treating stainless steel slag from an electric furnace, which includes loading molten slag into a slag pot, keeping the slag in a molten state by heat preservation, and then pouring molten blast furnace slag into a slag pot, stirring to evenly mix the slag with the blast furnace slag, and slowly cooling the mixed slag after a period of time and then heat-braising to obtain tailings. This method requires a long processing time to ensure that Cr is completely solidified in the slag, and the slag pot needs to be supplemented with heat and heat preservation, which increases the process and consumes extra energy.

[0007] Chinese patent publication number CN102559960 discloses a slag treatment method, which directly mixes hot converter slag and blast furnace slag in a certain proportion in an electric arc furnace, fully reacts the basic oxides and acidic oxides in the slag at a certain temperature, and forms glassy solid slag after rapid cooling. However, during the process of melting and mixing slag and blast furnace slag in an electric arc furnace, the iron oxides in the slag will be reduced to metallic iron by graphite carbon, causing the slag to dry out, thereby prolonging the digestion time and reducing the digestion efficiency, and the arc furnace arcing heating consumes additional energy.

[0008] Chinese patent publication number CN102492792 discloses a method for tempering and modifying molten steel slag, wherein 1500°C-1700°C molten steel slag discharged from converter steelmaking, 1400°C-1550°C blast furnace slag and lime powder are tempered and modified in an insulated slag bag. This method can improve the gelling activity of the steel slag, but the lime powder added during the modification process will cause the modified slag to face new volume stability problems. At the same time, the slag bag needs to be kept warm for a long time, which increases energy consumption.

[0009] A Chinese patent with publication number CN106045347 discloses a method for melting and digesting free calcium oxide in converter steel slag. First, steel slag with a temperature of more than 1450°C is loaded into a slag discharge tank, and then blast furnace slag and silicon-containing waste with a temperature of more than 1400°C are added to the slag discharge tank. The free calcium oxide in the steel slag is compositely digested by the acidic substances in the blast furnace slag and SiO2 in the silicon-containing waste, and finally the modified steel slag is cooled by air cooling or water cooling. The digestion process proposed by this method is carried out in a slag discharge tank without supplementary heat. The addition of cold silicon-containing waste and heat loss will inevitably reduce the slag temperature, thereby affecting the reaction rate between alkaline oxides and acidic oxides, and further affecting the digestion efficiency. At the same time, the digestion process takes a certain amount of time, which affects the connection between processes.

[0010] It is hoped to provide an improved method for disposing steel slag using an ironmaking system, particularly a method for eliminating free calcium oxide in steel slag and improving the gelling activity of steel slag, so as to achieve efficient resource utilization of steel slag. Summary of the invention

[0011] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides a method for treating steel slag using an ironmaking system, the purpose of which is to eliminate free calcium oxide in the steel slag and improve the gelling activity of the steel slag.

[0012] In order to achieve the above object, the technical solution adopted by the present invention is: a method for disposing steel slag using an ironmaking system, comprising the steps of:

[0013] S1, placing the steel slag above the blast furnace tapping channel and using the waste heat to preheat the steel slag;

[0014] S2, 20-30 minutes after the blast furnace slag iron is tapped, the preheated steel slag is evenly added to the liquid slag iron produced in the blast furnace slag iron tapping process to form a molten mixed slag in the main iron groove section;

[0015] Wherein, in step S2, the slag adding position is located in the main iron channel section 2-4m away from the blast furnace tapping hole.

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

[0017] In the step S2, the mass of the added steel slag does not exceed 50% of the mass of the liquid slag iron produced in one blast furnace slag iron tapping process.

[0018] In step S2, the slag adding speed is Among them, δ is the speed coefficient, which is 1.20-1.40, Q is the mass of liquid slag discharged from the blast furnace per unit time, k is the ratio of the weight of added slag to the weight of liquid slag produced in one blast furnace slag tapping process, and μ is the slag ratio, that is, the mass of molten slag produced by producing one ton of molten iron.

[0019] The mass of liquid slag and iron discharged from the blast furnace per unit time Among them, d is the average diameter of the iron mouth; g is the gravitational acceleration constant; h is the liquid level difference of the center line of the iron mouth outlet; l is the depth of the iron mouth; P is the pressure in the blast furnace; λ is the friction coefficient of the iron mouth wall; ρ is the average density of liquid slag iron.

[0020] The method for treating steel slag by using an ironmaking system of the present invention has the following beneficial effects:

[0021] (1) The present invention continuously and evenly adds steel slag into the main iron channel of the blast furnace. At this time, the temperature of the liquid slag is high, and the sensible heat of the liquid molten slag can be fully utilized to make the steel slag and the molten slag fully react, fully eliminate the free calcium oxide in the steel slag, and improve the gelling activity of the steel slag.

[0022] (2) The present invention adds steel slag during the blast furnace slag tapping process. At this time, the liquid slag is in a turbulent fluid state with good dynamic conditions. The steel slag can fully contact with the liquid slag, thereby improving the reaction speed and reaction degree between the steel slag and the blast furnace slag.

[0023] (3) The steel slag treated by the present invention can be the original slag after the existing steel slag primary treatment process, or the tailings after iron selection, which has stronger applicability. At the same time, the steel slag particle size is controlled below 5 mm, and can be steel slag particles or steel slag powder, so that it can fully react with high-temperature molten slag iron, thereby improving the digestion efficiency.

[0024] (4) The present invention does not add new processes, has a simple process, is pollution-free during the treatment process, has low cost, and has significant economic and social benefits, and has important practical significance for promoting the resource utilization of steel slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] This specification includes the following drawings, which show the following contents:

[0026] Figure 1 It is a process flow chart of the method for co-disposing steel slag by utilizing the blast furnace slag iron tapping process of the present invention. DETAILED DESCRIPTION

[0027] The specific implementation methods of the present invention are further explained in detail below by describing the embodiments with reference to the accompanying drawings, with the aim of helping those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention and facilitating its implementation.

[0028] like Figure 1 As shown, the present invention provides a method for co-disposing steel slag by utilizing the blast furnace slag iron process, comprising the following steps:

[0029] S1, placing the steel slag above the blast furnace tapping channel and using the waste heat to preheat the steel slag;

[0030] S2, 20-30 minutes after the blast furnace slag iron is tapped, the preheated steel slag is evenly added to the liquid slag iron produced in the blast furnace slag iron tapping process to form a molten mixed slag in the main iron groove section;

[0031] S3, treatment of the molten mixed slag by a water quenching treatment system;

[0032] S4. After cooling, water-quenched slag is obtained.

[0033] Specifically, the present invention aims at the problems of slow free calcium oxide digestion speed, limited slag processing volume, new processes and energy consumption in the process of steel slag modification and resource utilization, and proposes a method for treating steel slag using an ironmaking system. The steel slag is directly and evenly added to the molten slag in the main iron ditch of the blast furnace. During the turbulent flow of the high-temperature slag, the steel slag fully reacts with the liquid slag. Since the liquid slag has a high temperature and is in a turbulent state, the digestion speed of alkaline oxides such as free calcium oxide can be greatly improved, and the slag processing volume can be increased. This method does not add new processes, does not increase energy consumption, has a simple process, is pollution-free during the treatment process, and has low cost.

[0034] The working principle of the method of the present invention is as follows: steel slag is directly added to the liquid slag in the main iron ditch section of the blast furnace. In the turbulent process of the high-temperature liquid slag, the steel slag and the liquid slag fully react, wherein the iron oxides in the steel slag can be reduced by the carbon dissolved 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 generate silicates. The molten mixed slag formed after the reaction enters the water quenching treatment system through the slag ditch, and finally the water-quenched slag is obtained, which can be used for cement production.

[0035] In the above step S2, steel slag is directly added into the main iron ditch section, which is used for slag separation and molten iron diversion during the blast furnace slag tapping process. Liquid slag discharged from the blast furnace enters from the inlet of the main iron ditch section. After the liquid slag is mixed with the steel slag and fully reacts, the slag flows to the slag ditch after passing through the slag skimmer.

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

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

[0038] In the above step S2, steel slag is added continuously and evenly, and the mass of the added steel slag does not exceed 50% of the mass of liquid slag produced in one blast furnace slag tapping process (i.e., the ratio of the weight of the added steel slag to the weight of the liquid slag produced in one blast furnace slag tapping process, represented by k).

[0039] In the above step S2, steel slag is added continuously and evenly. The speed of adding steel slag (v: the mass of steel slag added per unit time) is related to the mass Q of slag iron discharged per unit time, the slag ratio μ (i.e. the mass of molten slag produced by producing one ton of molten iron) and the mass ratio k of steel slag added, which is specifically calculated as follows:

[0040]

[0041] Wherein, δ is the speed coefficient, which is 1.20-1.40; k is the ratio of the weight of added slag to the weight of liquid slag produced in one blast furnace slag tapping process; μ is the slag ratio (i.e., the mass of molten slag produced in producing one ton of molten iron); Q represents the speed of blast furnace discharge of liquid slag, i.e., the mass of liquid slag discharged from the blast furnace per unit time, which can be calculated using formula (2).

[0042]

[0043] Wherein, d is the average diameter of the blast furnace iron mouth; g is the gravitational acceleration constant; h is the liquid level difference of the center line of the blast furnace iron mouth outlet; l is the depth of the blast furnace iron mouth; P is the pressure inside the blast furnace; λ is the friction coefficient of the blast furnace iron mouth wall; ρ is the average density of liquid slag iron.

[0044] Take a steel plant with a capacity of 3200m 3 The blast furnace of was taken as the object (slag ratio μ=360kg / t, slag iron discharge speed Q=11.56t / min), and the blast furnace slag produced in its smelting process and the converter hot stewed steel slag were selected as 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 <![CDATA[SiO2]]> MgO <![CDATA[Al2O3]]> FeO MnO <![CDATA[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 slag (%)

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

[0049] Embodiment 1:

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

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

[0052] Embodiment 2:

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

[0054] The activity of the water-quenched slag powder and the strength of the mortar cut block were tested according to the national standards (GB / T 18046-2017 and GB / T 17671-2021), and the results are shown in Table 3. The 7-day activity index of the water-quenched slag powder is 86.31%, and the 28-day activity index is 97.36%. The 7-day compressive strength of the mortar cut block is 29.89 MPa, and the 28-day compressive strength is 54.99 MPa, which meets the requirements of S95 slag powder and meets the requirements of cement materials for construction.

[0055] Embodiment 3:

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

[0057] In this embodiment, the activity of the water-quenched slag powder and the strength of the mortar cut block are tested according to the national standards (GB / T 18046-2017 and GB / T 17671-2021), 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 cut block 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 cement materials for construction.

[0058] Embodiment 4:

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

[0060] The activity of the water-quenched slag powder and the strength of the mortar cut block were tested according to the national standards (GB / T 18046-2017 and GB / T 17671-2021), and the results are shown in Table 3. The 7-day activity index of the water-quenched slag powder is 84.12%, and the 28-day activity index is 97.07%. The 7-day compressive strength of the mortar cut block 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 cement materials for construction.

[0061] Embodiment 5:

[0062] In this embodiment, during the blast furnace ironmaking and slag tapping process, the preheated slag is added to the liquid slag in the main iron channel area 2m away from the blast furnace tapping port, the added mass of the converter slag is 50% of the mass of the liquid slag produced in the blast furnace slag tapping process, the slag adding rate is 1.84t / min, and the slag used is the iron selected slag in Table 2, and the slag particle size is less than 3mm. After the blast furnace main iron channel section, slag channel section and water quenching treatment, the water-quenched slag is obtained. After detection and analysis, the free calcium oxide content in the water-quenched slag is 0.59%, and the glass content is 89.68%.

[0063] The activity of the water-quenched slag powder and the strength of the mortar cut block were tested according to the national standards (GB / T 18046-2017 and GB / T 17671-2021), 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 cut block 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 cement materials for construction.

[0064] Table 3 Activity index of water-quenched slag powder and mortar cutting strength in the examples

[0065]

[0066] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for disposing steel slag using an ironmaking system, characterized in that: Includes steps: S1, placing the steel slag above the blast furnace tapping channel and using the waste heat to preheat the steel slag; S2, 20-30 minutes after the blast furnace slag iron is tapped, the preheated steel slag is evenly added to the liquid slag iron produced in the blast furnace slag iron tapping process to form a molten mixed slag in the main iron groove section; Wherein, in step S2, the slag adding position is located in the main iron channel section 2-4m away from the blast furnace tapping hole.

2. The method for co-disposing slag by utilizing the blast furnace slag iron process according to claim 1, characterized in that: The particle size of the steel slag is controlled to be below 5 mm.

3. The method for co-disposing slag by utilizing the blast furnace slag iron process according to claim 1, characterized in that: In the step S2, the mass of the added slag does not exceed 50% of the mass of the liquid molten blast furnace slag produced in one blast furnace slag tapping process.

4. The method for co-disposing slag in a blast furnace slag iron process according to any one of claims 1 to 3, characterized in that: In step S2, the slag adding speed is Among them, δ is the speed coefficient, which is 1.20-1.40, Q is the mass of liquid slag discharged from the blast furnace per unit time, k is the ratio of the weight of added slag to the weight of liquid slag produced in one blast furnace slag tapping process, and μ is the slag ratio, that is, the mass of molten slag produced by producing one ton of molten iron.

5. The method for co-disposing slag by utilizing the blast furnace slag iron process according to claim 4, characterized in that: The mass of liquid slag and iron discharged from the blast furnace per unit time Among them, d is the average diameter of the iron mouth; g is the gravitational acceleration constant; h is the liquid level difference of the center line of the iron mouth outlet; l is the depth of the iron mouth; P is the pressure in the blast furnace; λ is the friction coefficient of the iron mouth wall; ρ is the average density of liquid slag iron.

6. The method for co-disposing steel slag by utilizing the blast furnace slag iron process according to any one of claims 1 to 5, characterized in that: In the step S2, the weight of the added slag is 10% of the weight of the liquid slag produced in the blast furnace slag tapping process, and the slag adding speed is 0.30 t / min.

7. The method for co-disposing steel slag by utilizing the blast furnace slag iron process according to any one of claims 1 to 5, characterized in that: In the step S2, the weight of the added slag is 20% of the weight of the liquid slag produced in the blast furnace slag tapping process, and the slag adding speed is 0.65 t / min.

8. The method for co-disposing steel slag by utilizing the blast furnace slag iron process according to any one of claims 1 to 5, characterized in that: In the step S2, the weight of the added slag is 30% of the weight of the liquid slag produced in the blast furnace slag tapping process, and the slag adding speed is 0.95 t / min.

9. The method for co-disposing slag by utilizing the blast furnace slag iron process according to any one of claims 1 to 5, characterized in that: In the step S2, the weight of the added slag is 40% of the weight of the liquid slag produced in the blast furnace slag tapping process, and the slag adding speed is 1.25 t / min.

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