A slow-setting cold-bonded pellet with improved pellet strength and a preparation method and application thereof

Abstract

The application discloses a kind of slow setting type cold solidification pellets for improving pellet strength and its preparation method and application, belong to pellet preparation technical field.The method of the application includes the following steps:Step one, steel slag pore-forming pretreatment, obtain porous steel slag;Step two, prepare balling material: steel slag and metallurgical sludge are uniformly mixed according to a specific ratio, divided into A material, B material, C material three parts, no retarder is added in A material, retarder is added in B material and C material, and the amount of retarder added in B material is less than that in C material;Step three, layered balling: mainly divided into three-layer structure, inner layer uses A material, middle layer uses B material, outer layer uses C material, and is pressed into green ball in batches;Step four, industrial waste gas is introduced, and the green ball is carbonated and solidified to obtain cold solidification pellets.The method of the application can effectively solve the problem of uneven and insufficient carbonation of cold solidification pellets using industrial waste gas, thereby further improving the strength of the obtained pellets.

Description

Technical Field

[0001] This invention belongs to the field of pellet preparation technology, and more specifically, relates to a retarded cold-consolidated pellet for improving pellet strength, its preparation method and application. Background Technology

[0002] Cold-bonded pelletizing is a process that uses a binder to undergo a physical-chemical reaction to solidify iron ore particles. The resulting cold-bonded pellets are then processed in a rotary hearth furnace to produce metallized products, which can be added to blast furnaces, converters, and other processes. Cement and water glass are common binders for cold-bonded pellets. They utilize calcium silicate, sodium silicate, and other silica-containing calcium and magnesium minerals to absorb CO2 from the air. During this process, a carbonation reaction occurs with the CO2, thereby increasing the solidification strength of the pellets.

[0003] Taking dicalcium silicate (C2S) as an example, the carbonation reaction mainly consists of three steps: (1) CO2 is adsorbed and dissolved in the water layer on the particle surface to generate H2CO3; (2) H + It reacts with C2S to produce soluble Ca 2+ and silica gel (H4SiO4); (3) Ca 2+ With HCO3 - The reaction forms a CaCO3 layer on the particle surface. Numerous studies have shown that the CaCO3 product layer inhibits HCO3 production to some extent. - H + and Ca 2+ The diffusion of ions reduces the carbonization reaction rate.

[0004] It is worth noting that the steel industry accounts for approximately 8% of global carbon dioxide emissions annually, and this figure is expected to rise rapidly with increasing crude steel production. Statistics show that on average, producing one ton of crude steel generates about two tons of CO2 emissions and 600 kg of slag. In the long term, CO2 emission reduction and comprehensive utilization of solid waste in the steel industry have received widespread attention.

[0005] The applicant's research found that during the preparation of cold-set pellets, industrial flue gas containing a certain concentration of CO2 can be introduced into the green pellets. Compared to the existing method of using air for pellet carbonation, the industrial flue gas contains a relatively high concentration of CO2, which can increase the carbonation rate of the pellets. However, further research by the applicant revealed that the introduction of industrial flue gas also resulted in uneven and insufficient carbonation of the pellets, thus affecting the strength of the resulting cold-set pellets to some extent. To solve the above problems, there is an urgent need for a retarded cold-set pellet and its preparation method that can improve the uniformity and strength of pellet carbonation. Summary of the Invention

[0006] 1. The problem to be solved

[0007] Firstly, the purpose of this invention is to provide a slow-setting cold-solidified pellet and its preparation method that can improve the uniformity and strength of pellet carbonation. This can effectively solve the problem of uneven and insufficient carbonation of cold-solidified pellets using industrial waste gas, thereby further improving the strength of the obtained pellets.

[0008] Secondly, this invention also provides an application for the cold-consolidated pellets prepared by the above method. These pellets are placed in a rotary hearth furnace for roasting. During roasting, zinc-containing dust within the furnace can be treated, and the resulting metallized pellets can be used as a converter coolant. This invention not only achieves the resource utilization of industrial flue gas and metallurgical solid waste but also enables carbon emission reduction in the steel industry.

[0009] 2. Technical Solution

[0010] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0011] Firstly, the present invention provides a retarded cold-consolidated pellet for improving pellet strength. The cold-consolidated pellet comprises a three-layer structure, consisting of an inner layer, a middle layer, and an outer layer from the inside out. The components of the three-layer pellet structure all include steel slag and metallurgical dust. The middle layer and the outer layer components each contain additional retarder, and the mass percentage of the retarder in the middle layer component is less than the mass percentage of the retarder in the outer layer component.

[0012] It should be noted that using industrial waste gas for carbonation treatment of pellets, compared to room temperature air, can utilize the high CO2 content and certain temperature and humidity of industrial waste gas, which can increase the carbonation reaction rate of the pellets and thus significantly shorten the time of natural carbonation. However, this also brings new problems. When using industrial waste gas to carbonate pellets, there is a difference in the carbonation reaction rate between the surface and the interior of the pellets. This difference in reaction rate will cause the components near the surface of the pellets to undergo carbonation reaction first. Carbonation products can easily block the CO2 entry channels, making it difficult for CO2 to pass into the interior of the pellets. This can easily lead to stratification of the pellets, resulting in insufficient and uneven carbonation. To a certain extent, this affects the strength of the resulting cold-bonded pellets. In order to coordinate the carbonation reaction process inside and outside the pellets and achieve a better match between the carbonation reaction rates inside and outside the pellets, it is possible to effectively improve the uneven reaction phenomenon and further improve the overall strength of the cold-bonded pellets. This invention adds a suitable retarder to the pellets and optimizes the method of adding the retarder. The proportion of retarder added to the outer layer of the pellets is higher than that to the middle layer. This slows down the setting speed of the outer layer, slightly slows down the setting speed of the middle layer, and allows the inner layer to set normally. Ultimately, this ensures that the setting time of the inner and outer layers of the pellets is consistent, achieving the best setting effect.

[0013] As a further improvement of this invention, the applicant has discovered through extensive research that the ratio of retarder in the outer and middle layers has a significant impact on the coagulation effect. To ensure the overall retarding effect of the pellets, the mass ratio of retarder in the outer layer component is 2 to 4 times that in the middle layer component, and the amount of retarder added in the middle layer accounts for 0.5% to 1.0% of the total mass of the middle layer component. This design can coordinate the coagulation speed of the outer, middle, and inner layer raw materials to remain consistent. Since the pellet can be regarded as an unreacted core model, the outer layer raw materials first come into contact with CO2 and undergo carbonation reaction. The carbonation reaction rate decreases step by step from the outer layer to the core. By reasonably adding retarder, it is possible to avoid the outer layer raw materials from coagulating too quickly due to flue gas injection, causing pore blockage, making it difficult for CO2 in the environment to enter the interior and undergo carbonation reaction, thus resulting in uneven and insufficient pellet strength.

[0014] In addition, the retarder is desulfurized ash or desulfurized gypsum, whose main components are CaSO3, CaSO4, etc., which can slow down the hydration rate of substances such as C2S and C3S in steel slag, but does not affect the final carbonation result, thus promoting the uniformity of the carbonation reaction.

[0015] As a further improvement of the present invention, the inner diameter of the pellet is 6-8 mm, and the thickness of the middle layer and the outer layer are both 3-4 mm.

[0016] As a further improvement of the present invention, the components of the three-layer pellet structure also include alkali-containing dust, which is pre-filled into the pores on the surface of the steel slag. By filling the steel slag with alkali-containing dust, it is beneficial to produce alkali-activated steel slag. The alkaline oxides such as K2O and Na2O contained in the alkali-containing dust react with water in the pores on the surface of the steel slag to form an alkaline environment. The alkaline substances produced can promote the hydration reaction of silicates in the steel slag and accelerate the formation of gel substances. These gels can fill the pores of the raw material particles, thereby further improving the strength of the cold-bonded pellets.

[0017] Secondly, the preparation method of the above-mentioned retarded cold-consolidated pellets of the present invention is characterized by comprising the following steps:

[0018] Step 1: Pre-treatment of steel slag to create porous steel slag;

[0019] Step 2: Preparation of pelletizing material;

[0020] Prepare the inner layer pelletizing material, the middle layer pelletizing material and the outer layer pelletizing material respectively, which correspond to material A, material B and material C respectively, for later use;

[0021] Step 3: Layered ball formation:

[0022] The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 6-8 mm. Then material B is added and pressed to form an intermediate layer with a thickness of 3-4 mm. Finally, material C is added and pressed to form an outer layer with a thickness of 3-4 mm.

[0023] Step 4: Introduce industrial waste gas to carbonate and solidify the green pellets, resulting in cold-solidified pellets.

[0024] As a further improvement of the present invention, the mass ratio of steel slag to metallurgical dust in the pelletizing material is 1:(10-20).

[0025] No retarder is added to component A. The amount of retarder added to component B is 0.5% to 1.0% of the total mass of component B required. The amount of retarder added to component C is 1.0% to 4.0% of the total mass of component C required.

[0026] As a further improvement of the present invention, in step one, the steel slag is ground to a particle size of -0.149mm with a mass percentage content of ≥95%, and then the steel slag is immersed in an acidic solution for pickling, controlling the free CaO content to decrease to 0.1%-0.3%. Specifically, in the pickling process of the steel slag, by reducing the free CaO content in the steel slag to 0.1%-0.3%, the decrease in f-CaO content means that f-CaO is leached out, the pores become more numerous, which facilitates subsequent carbonation. However, the f-CaO content cannot be reduced too low, as an excessively low f-CaO content will lead to a decrease in the strength and brittleness of the steel slag itself. Therefore, in the present invention, controlling the f-CaO content in the range of 0.1%-0.3% is superior. During acid pickling and pore formation, a mixed solution of formic acid and acetic acid is used, with a formic acid:acetic acid molar ratio of 1:(0.5~2)mol / L. This treatment method solves the shortcomings of poor stability and low activity of steel slag as a binder. The resulting porous steel slag can effectively increase the specific surface area of ​​steel slag and the contact points between CO2 and effective components such as silicates, enhance carbonation efficiency, and thus improve the strength of cold-bonded pellets and CO2 emission reduction efficiency.

[0027] Furthermore, the metallurgical dust in the pelletizing material is blast furnace ash or OG mixed dust, and the metallurgical dust has a particle size of -0.074mm and a mass percentage content of ≥80%.

[0028] As a further improvement of the present invention, the metallurgical dust and sludge is a combination of blast furnace ash and OG mixed dust and sludge, with a mass ratio of blast furnace ash to OG mixed dust and sludge of 1:(3-4). The cold-bonded pellets produced by the present invention need to contain a certain amount of carbon for use in the reduction reaction of iron oxide and zinc oxide. A suitable ratio of blast furnace ash to OG mixed dust and sludge is beneficial to the final quality of the pellets.

[0029] As a further improvement of the present invention, when the porous steel slag is filled with alkali-containing dust, the alkali-containing dust is sintering machine head ash, which is ground to a particle size of -13μm and has a mass percentage content of ≥95%. The mass ratio of alkali-containing dust to steel slag is (0.04~0.10):1, and the mixing time is 10~30min. The main chemical components and mass percentages of the sintering machine head ash are: TFe: 20~40%, K2O: 3~12%, Na2O: 0.2~8.0%, and other unavoidable impurities. More optimally, under the addition amount of the present invention, it is better to control the sum of K2O and Na2O components in the sintering machine head ash to be between 10% and 20% of the total components, which can ensure the improvement of steel slag activity without causing a decrease in the strength of the prepared cold-bonded pellets.

[0030] As a further preferred embodiment of the present invention, in step four, the green pellets are placed in a curing chamber, and industrial waste gas is introduced for carbonation and solidification. The industrial waste gas is sintering flue gas or rotary hearth furnace flue gas, and the flow rate of the introduced industrial waste gas is 30,000 to 80,000 m / s. 3 The treatment time is 3-12 hours, with a temperature of 150-220℃, a CO2 concentration of 4-8wt%, a CO content of 0.3-2wt%, a water content of 4-8wt%, and a treatment duration of 3-12 hours.

[0031] Furthermore, it is worth noting that controlling the particle size of the sintering machine head ash to the -13μm range allows the sintering machine head ash to have a larger specific surface area, making it easier to enter and adsorb into the pores of the porous steel slag surface. This results in more thorough contact with the active substances inside the steel slag. If the particle size is too large, the sintering machine head ash particles cannot fill the pores of the steel slag. If the particle size is too small, the specific surface area of ​​the sintering machine head ash is too large, which can easily lead to self-agglomeration and a decrease in the filling effect. By filling the sintering machine head ash, compared to steel slag without sintering machine head ash, the hydration process of substances such as calcium silicate inside the steel slag can be accelerated, forming more gel substances, thereby improving the strength of cold-consolidated pellets. Using the technical solution of this invention, the strength of the cold-consolidated pellets prepared is above 210 N / Pellet when the steel slag pores in the cold-consolidated pellets are not filled with alkali-containing dust; when the steel slag pores in the cold-consolidated pellets are filled with alkali-containing dust, the strength is above 285 N / Pellet. Compared with cold-consolidated pellets without added retarder, the overall strength of the pellets is significantly improved.

[0032] Thirdly, in the application of the above-mentioned slow-setting cold-consolidated pellets of the present invention, the slow-setting cold-consolidated pellets are placed in a rotary hearth furnace for drying and calcination. The drying temperature is 150-250℃, the drying time is 5-10 min, and the calcination temperature is 1250-1350℃, the calcination time is 15-25 min. Through this treatment, on the one hand, the zinc-containing dust in the rotary hearth furnace can be treated; on the other hand, metallized finished pellets that can be used as a coolant in the converter can be produced.

[0033] 3. Beneficial effects

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) The present invention provides a retarded cold-bonded pellet, which first acid-porositizes steel slag to enhance its activity and produce porous steel slag, and then pelletizes it with metallurgical dust and sludge. At the same time, a layered pelletizing process is adopted in the pelletizing process to produce pellets with a three-layer structure, including an inner layer, a middle layer and an outer layer. In this process, a retarder is added to the components of the middle layer and the outer layer, and the mass ratio of the retarder in the middle layer component (i.e., the retarder addition concentration) is lower than that in the outer layer component. Thus, when industrial flue gas is introduced, the carbonation reaction rate inside the pellet can be coordinated, and the problem of the overall strength of the pellet being reduced due to the uncoordinated carbonation rate between the surface and the inside of the pellet, which would cause the outer layer to complete carbonation first and hinder the carbonation inside the pellet.

[0036] (2) Another type of retarded cold-bonded pellets provided by this invention involves acid-induced pore formation of steel slag followed by further mixing with sintering machine head ash to produce alkali-activated active steel slag, which further enhances the activity of the steel slag. This alkali-activated active steel slag is then used to make pellets with metallurgical dust and sludge, and a layered pelletizing process is employed during the pelletizing process to produce pellets with a three-layer structure, including an inner layer, a middle layer, and an outer layer. A retarder is added to the components of the middle and outer layers, and the mass percentage of the retarder in the middle layer components (i.e., the amount of retarder added) is... The concentration of the retarder is lower than the mass ratio of the retarder in the outer layer. On the one hand, after adding the retarder, when the pellets are subsequently fed with industrial flue gas for carbonation, it can ensure that the carbonation inside and outside the pellets is uniform, thus improving the uniformity and sufficiency of carbonation. On the other hand, compared with the retarded cold-solidified pellets made from steel slag without sintering head ash, the strength of the cold-solidified pellets obtained by adding sintering head ash is further improved, and the time for carbonation of steel slag particles is further shortened.

[0037] (3) The retarder used in the slow-setting cold-setting pellets of the present invention is desulfurized ash and desulfurized gypsum. The main component of desulfurized ash is CaSO4, which can slow down the hydration rate of substances such as C2S and C3S in steel slag, but does not affect the final carbonation result, thus promoting the uniformity of the carbonation reaction.

[0038] (4) The main raw materials of the slow-setting cold-consolidated pellets of the present invention are steel slag, metallurgical dust, desulfurization ash and sintering machine head ash (finally, industrial waste gas is introduced for carbonation treatment, and all are made by using metallurgical solid waste or industrial waste gas to make cold-consolidated pellets, which not only significantly reduces the manufacturing cost of existing cold-consolidated pellets (in the prior art, additional binders are usually required when preparing cold-consolidated pellets, while the present invention uses modified steel slag to replace binders for preparation), but also improves the resource utilization efficiency of industrial solid waste. In addition, it also provides a good way for the dissolution and treatment of industrial waste. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the spherical cold-bonded pellet structure of the present invention;

[0040] Figure 2 This is a schematic diagram of the ellipsoidal cold-bonded pellet structure of the present invention;

[0041] Figure 3 This is a schematic diagram of the structure of the carbonated porous steel slag particles in this invention;

[0042] Figure 4 This is a schematic diagram of the structure of the carbonized steel slag particles filled with alkali-containing dust in this invention.

[0043] Figure 5 This is a schematic diagram of the preparation method of the cold-bonded pellets (without alkali-containing dust) and metallized finished pellets of the present invention;

[0044] Figure 6 This is a schematic diagram of the preparation method of another type of cold-bonded pellets (filled with alkali-containing dust) and metallized finished pellets according to the present invention;

[0045] In the picture:

[0046] 1. Inner layer; 2. Middle layer; 3. Outer layer; 4. Steel slag; 401. Pores; 5. Hydration layer; 6. Carbonation layer; 7. Alkali-containing dust. Detailed Implementation

[0047] The structural diagram of the retarded cold-consolidated pellets implemented in this embodiment is as follows: Figure 1 As shown, it comprises a three-layer structure, consisting of an inner layer 1, a middle layer 2, and an outer layer 3 from the inside out. The pelletizing material components of the three-layer pelletizing structure all include steel slag and metallurgical dust. Both the middle layer 2 and the outer layer 3 pelletizing material components contain additional retarder, and the mass proportion of the retarder in the middle layer 2 pelletizing material component is less than that in the outer layer 3 component. Specifically, the mass proportion of the retarder in the outer layer 3 pelletizing material component is 2 to 4 times that of the middle layer 2 pelletizing material component. The retarder used is desulfurized ash or desulfurized gypsum.

[0048] The inner layer 1 of the pellet has a diameter of 6-8 mm, and the thicknesses of the middle layer 2 and outer layer 3 are both 3-4 mm. Furthermore, it should be noted that, to improve pelletizing convenience and facilitate pellet demolding during layered pelletizing, this cold-consolidated pellet can also be designed as follows: Figure 2 The ellipsoidal structure shown in the diagram has an equivalent diameter of 6-8 mm for the inner layer 1 when it is pressed into an ellipsoidal structure, and a thickness of 3-4 mm for both the middle layer 2 and the outer layer 3.

[0049] Furthermore, it is worth noting that the steel slag particles after carbonation treatment in this embodiment are as follows: Figure 3 and Figure 4 Two structural forms. Specifically, such as... Figure 3 As shown, the inside of the steel slag particles is a porous steel slag 4, that is, after acid pore-forming of the steel slag, a steel slag 4 with pores 401 is formed. The outside of the steel slag 4 is a hydration layer 5, which is mainly composed of H4SiO4 gel. The outside of the hydration layer 5 is a carbonation layer 6, which is mainly composed of CaCO3.

[0050] In addition, to further enhance the activity of steel slag, a schematic diagram of another structural form of steel slag particles is shown below. Figure 4 As shown, the holes 401 on the surface of the steel slag 4 are filled with alkali-containing dust (i.e., sintering machine head ash).

[0051] For ease of description, the steel slag composition used in the following examples is as follows: CaO: 49.90%, Fe2O3: 24.52%, SiO2: 11.67%, MgO: 3.94%, MnO: 2.13%, P2O5: 2.54%, Al2O3: 2.90%, TiO2: 1.27%, with the remainder being unavoidable impurities.

[0052] The chemical composition and mass percentage of the sintering machine head ash are TFe: 32.5%, K2O: 8.122%, Na2O: 3.420%, and other unavoidable impurities.

[0053] The present invention will be further described below with reference to specific embodiments.

[0054] Example 1-1

[0055] like Figure 6 As shown, the preparation method of the retarded cold-consolidated pellets in this embodiment includes the following steps:

[0056] (1) Steel slag hole-making pretreatment to obtain porous steel slag;

[0057] In this embodiment, a certain amount of steel slag, sintering machine head ash, and metallurgical dust were weighed out at a mass ratio of 1:0.06:15 and set aside for later use. First, the steel slag was placed in a ball mill and ground to fine particles, controlling the mass percentage content of steel slag particles with a size of -0.149mm to be ≥95%. Then, a mixed solution of formic acid and acetic acid (molar concentration ratio of formic acid and acetic acid is 1:1.2mol / L) was added for acid washing, controlling the free CaO content to decrease to 0.2%, thus producing porous steel slag.

[0058] (2) Preparation of alkali-activated steel slag;

[0059] Alkali-containing dust is ground to a particle size of -13μm with a mass percentage content of ≥95%, and then mixed with porous steel slag by air for 20 minutes to obtain alkali-activated steel slag.

[0060] (3) Preparation of pelleting material;

[0061] Alkali-activated steel slag and metallurgical dust (i.e., a mixture of blast furnace ash and OG mixed dust in a mass ratio of 1:3.5) were mixed evenly and used as pelletizing material. The mixture was divided into three parts, labeled as material A, material B, and material C. 0.75% desulfurization ash was added to material B and 2.5% desulfurization ash was added to material C for later use.

[0062] (4) Layered ball formation;

[0063] The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 7mm. Then material B is added and pressed to form an intermediate layer with a thickness of 3.5mm. Finally, material C is added and pressed to form an outer layer with a thickness of 3.5mm.

[0064] (5) Carbonation and solidification treatment of green pellets;

[0065] Sintering flue gas or rotary hearth furnace flue gas is introduced into the green pellets for carbonation and solidification treatment. The introduced industrial waste gas flow rate is 60,000 m / s. 3 The process involves a temperature of 180℃, a CO2 concentration of 6%, a moisture content of 6%, and a treatment time of 6 hours to obtain cold-consolidated pellets.

[0066] The obtained cold-consolidated pellets are dried and calcined to produce metallized finished pellets. The specific operation is as follows:

[0067] Dry at 200℃ for 5 minutes, then calcine at 1300℃ for 20 minutes to form pellets.

[0068] The performance of the obtained cold-consolidated pellets and the calcined metallized pellets was tested, and the test results are shown in Table 1.

[0069] Comparative Example 1-1

[0070] The preparation method of the cold-consolidated pellets in this comparative example differs from that in Example 1-1 in that: without the treatment in steps three and four, the alkali-activated active steel slag and metallurgical dust are directly mixed with water and pressed into pellets. The roller pressure is controlled at 25 MPa and the moisture content of the pellets is controlled at 14%. The remaining process operations and process parameters are the same as those in Example 1-1.

[0071] Comparative Examples 1-2

[0072] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 1-1 in that, in step three, 0.3% of desulfurization ash is added to material B.

[0073] Comparative Examples 1-3

[0074] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 1-1 in that, in step three, 1.5% of desulfurization ash is added to material B.

[0075] Comparative Examples 1-4

[0076] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 1-1 in that, in step three, 0.5% of desulfurization ash is added to material C.

[0077] Comparative Examples 1-5

[0078] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 1-1 in that, in step three, 5.0% of desulfurization ash is added to material C.

[0079] Comparative Examples 1-6

[0080] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 1-1 in that: in step three, 0.5% of desulfurization ash is added to material B, and 3.0% of desulfurization ash is added to material C.

[0081] Examples 1-2

[0082] The preparation method of the retarded cold-consolidated pellets in this embodiment includes the following steps:

[0083] (1) Steel slag hole-making pretreatment to obtain porous steel slag;

[0084] In this embodiment, a certain amount of steel slag, sintering machine head ash, and metallurgical dust were weighed out in a mass ratio of 1:0.04:10 and set aside for later use. First, the steel slag was placed in a ball mill and ground to fine particles, controlling the mass percentage content of steel slag particles with a size of -0.149mm to be ≥95%. Then, a mixed solution of formic acid and acetic acid (molar concentration ratio of formic acid and acetic acid is 1:2 mol / L) was added for acid washing, controlling the free CaO content to decrease to 0.25%, thus producing porous steel slag.

[0085] (2) Preparation of alkali-activated steel slag;

[0086] The alkali-containing dust is ground to a particle size of -13μm with a mass percentage content of ≥95%, and then mixed with porous steel slag by air for 10 minutes to obtain alkali-activated steel slag.

[0087] (3) Preparation of pelleting material;

[0088] Alkali-activated steel slag and metallurgical dust (i.e., a mixture of blast furnace ash and OG mixed dust in a mass ratio of 1:4) were mixed evenly and used as pelletizing material. The mixture was divided into three parts, labeled as material A, material B, and material C. 0.5% desulfurization ash was added to material B and 1.0% desulfurization ash was added to material C for later use.

[0089] (4) Layered ball formation;

[0090] The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 6mm. Then material B is added and pressed to form an intermediate layer with a thickness of 4mm. Finally, material C is added and pressed to form an outer layer with a thickness of 4mm.

[0091] (5) Carbonation and solidification treatment of green pellets;

[0092] Sintering flue gas or rotary hearth furnace flue gas is introduced into the green pellets for carbonation and solidification treatment. The introduced industrial waste gas flow rate is 30,000 m / s. 3 The treatment process was carried out at a temperature of 220℃, a CO2 concentration of 8%, a moisture content of 9%, and a treatment time of 9 hours, resulting in cold-consolidated pellets.

[0093] The obtained cold-consolidated pellets are dried and calcined to produce metallized finished pellets. The specific operation is as follows:

[0094] Dry at 150℃ for 10 minutes, then calcine at 1350℃ for 15 minutes to form pellets.

[0095] The performance of the obtained cold-consolidated pellets and the calcined metallized pellets was tested, and the test results are shown in Table 1.

[0096] Examples 1-3

[0097] The preparation method of the retarded cold-consolidated pellets in this embodiment includes the following steps:

[0098] (1) Steel slag hole-making pretreatment to obtain porous steel slag;

[0099] In this embodiment, a certain amount of steel slag, sintering machine head ash, and metallurgical dust were weighed out in a mass ratio of 1:0.1:20 and set aside for later use. First, the steel slag was placed in a ball mill and ground to fine particles, controlling the mass percentage content of steel slag particles with a size of -0.149 mm to be ≥95%. Then, a mixed solution of formic acid and acetic acid (molar concentration ratio of formic acid and acetic acid is 1:1.2 mol / L) was added for acid washing, controlling the free CaO content to decrease to 0.3%, thus producing porous steel slag.

[0100] (2) Preparation of alkali-activated steel slag;

[0101] Alkali-containing dust is ground to a particle size of -13μm with a mass percentage content of ≥95%, and then mixed with porous steel slag by air for 20 minutes to obtain alkali-activated steel slag.

[0102] (3) Preparation of pelleting material;

[0103] Alkali-activated steel slag and metallurgical dust (i.e., a mixture of blast furnace ash and OG mixed dust in a mass ratio of 1:3) were mixed evenly and used as pelletizing material. The mixture was divided into three parts, labeled A, B and C. 1.0% of desulfurization ash was added to B and 4.0% of desulfurization ash was added to C for later use.

[0104] (4) Layered ball formation;

[0105] The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 8mm. Then material B is added and pressed to form a middle layer with a thickness of 3mm. Finally, material C is added and pressed to form an outer layer with a thickness of 3mm.

[0106] (5) Carbonation and solidification treatment of green pellets;

[0107] Sintering flue gas or rotary hearth furnace flue gas is introduced into the green pellets for carbonation and solidification treatment. The introduced industrial waste gas flow rate is 50,000 m / s. 3 The process involves a temperature of 150℃, a CO2 concentration of 7%, a moisture content of 6%, and a treatment time of 3 hours to obtain cold-consolidated pellets.

[0108] The obtained cold-consolidated pellets are dried and calcined to produce metallized finished pellets. The specific operation is as follows:

[0109] Dry at 200℃ for 8 minutes, then calcine at 1300℃ for 20 minutes to form pellets.

[0110] The performance of the obtained cold-consolidated pellets and the calcined metallized pellets was tested, and the test results are shown in Table 1.

[0111] Examples 1-4

[0112] The preparation method of the retarded cold-consolidated pellets in this embodiment includes the following steps:

[0113] (1) Steel slag hole-making pretreatment to obtain porous steel slag;

[0114] In this embodiment, a certain amount of steel slag, sintering machine head ash, and metallurgical dust were weighed out at a mass ratio of 1:0.06:15 and set aside for later use. First, the steel slag was placed in a ball mill and ground to fine particles, controlling the mass percentage content of steel slag particles with a size of -0.149mm to be ≥95%. Then, a mixed solution of formic acid and acetic acid (molar concentration ratio of formic acid and acetic acid is 1:0.5mol / L) was added for acid washing, controlling the free CaO content to decrease to 0.1%, thus producing porous steel slag.

[0115] (2) Preparation of alkali-activated steel slag;

[0116] Alkali-containing dust is ground to a particle size of -13μm with a mass percentage content of ≥95%, and then mixed with porous steel slag by air for 30 minutes to obtain alkali-activated steel slag.

[0117] (3) Preparation of pelleting material;

[0118] Alkali-activated steel slag and metallurgical dust (i.e., a mixture of blast furnace ash and OG mixed dust in a mass ratio of 1:3.5) were mixed evenly and used as pelletizing material. The mixture was divided into three parts, labeled as material A, material B, and material C. 0.75% desulfurization ash was added to material B and 2.5% desulfurization ash was added to material C for later use.

[0119] (4) Layered ball formation;

[0120] The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 7mm. Then material B is added and pressed to form an intermediate layer with a thickness of 3.5mm. Finally, material C is added and pressed to form an outer layer with a thickness of 3.5mm.

[0121] (5) Carbonation and solidification treatment of green pellets;

[0122] Sintering flue gas or rotary hearth furnace flue gas is introduced into the green pellets for carbonation and solidification treatment. The introduced industrial waste gas flow rate is 80,000 m / s. 3 The process was carried out at a temperature of 190℃, a CO2 concentration of 4%, a water content of 4%, and a treatment time of 9 hours to obtain cold-consolidated pellets.

[0123] The obtained cold-consolidated pellets are dried and calcined to produce metallized finished pellets. The specific operation is as follows:

[0124] Dry at 200℃ for 5 minutes, then calcine at 1250℃ for 25 minutes to form pellets.

[0125] The performance of the obtained cold-consolidated pellets and the calcined metallized pellets was tested, and the test results are shown in Table 1.

[0126] Example 2-1

[0127] like Figure 5 As shown, the preparation method of the retarded cold-consolidated pellets in this embodiment includes the following steps:

[0128] (1) Steel slag hole-making pretreatment to obtain porous steel slag;

[0129] In this embodiment, a certain amount of steel slag and metallurgical dust were weighed out at a mass ratio of 1:15 and set aside for later use. First, the steel slag was placed in a ball mill and ground to a fine particle size, controlling the mass percentage content of steel slag particles with a size of -0.149 mm to be ≥95%. Then, a mixed solution of formic acid and acetic acid (molar concentration ratio of formic acid to acetic acid of 1:1.2 mol / L) was added for acid washing, controlling the free CaO content to decrease to 0.2%.

[0130] (2) Preparation of pelleting material;

[0131] After processing, the steel slag is mixed with metallurgical dust (i.e., a mixture of blast furnace ash and OG mixed dust in a mass ratio of 1:3.5) and used as pelletizing material. It is then divided into three parts, labeled as material A, material B, and material C. 0.75% of desulfurization ash is added to material B, and 2.5% of desulfurization ash is added to material C for later use.

[0132] (3) Layered ball formation;

[0133] The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 7mm. Then material B is added and pressed to form an intermediate layer with a thickness of 3.5mm. Finally, material C is added and pressed to form an outer layer with a thickness of 3.5mm.

[0134] (4) Carbonation and solidification treatment of green pellets;

[0135] Sintering flue gas or rotary hearth furnace flue gas is introduced into the green pellets for carbonation and solidification treatment. The introduced industrial waste gas flow rate is 60,000 m / s. 3 The process involves a temperature of 180℃, a CO2 concentration of 6%, a moisture content of 6%, and a treatment time of 6 hours to obtain cold-consolidated pellets.

[0136] The obtained cold-consolidated pellets are dried and calcined to produce metallized finished pellets. The specific operation is as follows:

[0137] Dry at 200℃ for 5 minutes, then calcine at 1300℃ for 20 minutes to form pellets.

[0138] The performance of the obtained cold-consolidated pellets and the calcined metallized pellets was tested, and the test results are shown in Table 1.

[0139] Comparative Example 2-1

[0140] The preparation method of the cold-bonded pellets in this comparative example differs from that in Example 2-1 in that: without the treatment in steps three and four, the treated steel slag and metallurgical dust are directly mixed, water is added, and the pellets are pressed into pellets. The roller pressure is controlled at 25 MPa, and the moisture content of the pellets is controlled at 14%. The remaining process operations and process parameters are the same as in Example 2-1.

[0141] Comparative Example 2-2

[0142] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 2-1 in that, in step three, 0.3% of desulfurization ash is added to material B.

[0143] Comparative Examples 2-3

[0144] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 2-1 in that, in step three, 1.5% of desulfurization ash is added to material B.

[0145] Comparative Examples 2-4

[0146] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 2-1 in that, in step three, 0.5% of desulfurization ash is added to material C.

[0147] Comparative Examples 2-5

[0148] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 2-1 in that, in step three, 5.0% of desulfurization ash is added to material C.

[0149] Comparative Examples 2-6

[0150] The method for preparing the cold-consolidated pellets in this comparative example differs from that in Example 2-1 in that: in step three, 0.5% of desulfurization ash is added to material B, and 3.0% of desulfurization ash is added to material C.

[0151] Example 2-2

[0152] The preparation method of the retarded cold-consolidated pellets in this embodiment includes the following steps:

[0153] (1) Steel slag hole-making pretreatment to obtain porous steel slag;

[0154] In this embodiment, a certain amount of steel slag and metallurgical dust were weighed out at a mass ratio of 1:12. The steel slag was first ground in a ball mill to a fine particle size, and the mass percentage content of the steel slag with a particle size of -0.149 mm was controlled to be ≥95%. Then, a mixed solution of formic acid and acetic acid (molar concentration ratio of formic acid to acetic acid of 1:2 mol / L) was added for acid washing, and the free CaO content was controlled to decrease to 0.25%.

[0155] (2) Preparation of pelleting material;

[0156] The treated steel slag is mixed with metallurgical dust (i.e., a mixture of blast furnace ash and OG mixed dust in a mass ratio of 1:4) and used as pelletizing material. It is then divided into three parts, labeled A, B, and C. 0.5% desulfurization ash is added to B and 1.0% desulfurization ash is added to C for later use.

[0157] (3) Layered ball formation;

[0158] The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 6mm. Then material B is added and pressed to form an intermediate layer with a thickness of 4mm. Finally, material C is added and pressed to form an outer layer with a thickness of 4mm.

[0159] (4) Carbonation and solidification treatment of green pellets;

[0160] Sintering flue gas or rotary hearth furnace flue gas is introduced into the green pellets for carbonation and solidification treatment. The introduced industrial waste gas flow rate is 30,000 m / s. 3 The process was carried out at a temperature of 220℃, a CO2 concentration of 8%, a water content of 9%, and a treatment time of 12 hours to obtain cold-consolidated pellets.

[0161] The obtained cold-consolidated pellets are dried and calcined to produce metallized finished pellets. The specific operation is as follows:

[0162] Dry at 150℃ for 10 minutes, then calcine at 1350℃ for 15 minutes to form pellets.

[0163] The performance of the obtained cold-consolidated pellets and the calcined metallized pellets was tested, and the test results are shown in Table 1.

[0164] Example 2-3

[0165] The preparation method of the retarded cold-consolidated pellets in this embodiment includes the following steps:

[0166] (1) Steel slag hole-making pretreatment to obtain porous steel slag;

[0167] In this embodiment, a certain amount of steel slag and metallurgical dust were weighed out at a mass ratio of 1:10 and set aside for later use. First, the steel slag was placed in a ball mill and ground to a fine particle size, controlling the mass percentage content of steel slag particles with a size of -0.149 mm to be ≥95%. Then, a mixed solution of formic acid and acetic acid (molar concentration ratio of formic acid to acetic acid of 1:1.2 mol / L) was added for acid washing, controlling the free CaO content to decrease to 0.3%.

[0168] (2) Preparation of pelleting material;

[0169] The treated steel slag is mixed with metallurgical dust (i.e., a mixture of blast furnace ash and OG mixed dust in a mass ratio of 1:3) and used as pelletizing material. It is then divided into three parts, labeled A, B, and C. 1.0% of desulfurization ash is added to B and 4.0% of desulfurization ash is added to C for later use.

[0170] (3) Layered ball formation;

[0171] The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 8mm. Then material B is added and pressed to form a middle layer with a thickness of 3mm. Finally, material C is added and pressed to form an outer layer with a thickness of 3mm.

[0172] (4) Carbonation and solidification treatment of green pellets;

[0173] Sintering flue gas or rotary hearth furnace flue gas is introduced into the green pellets for carbonation and solidification treatment. The introduced industrial waste gas flow rate is 50,000 m / s. 3 The process involves a temperature of 150℃, a CO2 concentration of 7%, a moisture content of 6%, and a treatment time of 4 hours to obtain cold-consolidated pellets.

[0174] The obtained cold-consolidated pellets are dried and calcined to produce metallized finished pellets. The specific operation is as follows:

[0175] Dry at 200℃ for 8 minutes, then calcine at 1300℃ for 20 minutes to form pellets.

[0176] The performance of the obtained cold-consolidated pellets and the calcined metallized pellets was tested, and the test results are shown in Table 1.

[0177] Examples 2-4

[0178] The preparation method of the retarded cold-consolidated pellets in this embodiment includes the following steps:

[0179] (1) Steel slag hole-making pretreatment to obtain porous steel slag;

[0180] In this embodiment, a certain amount of steel slag and metallurgical dust were weighed out at a mass ratio of 1:20 and set aside for later use. First, the steel slag was placed in a ball mill and ground to a fine particle size, controlling the mass percentage content of steel slag particles with a size of -0.149 mm to be ≥95%. Then, a mixed solution of formic acid and acetic acid (molar concentration ratio of formic acid to acetic acid of 1:0.5 mol / L) was added for acid washing, controlling the free CaO content to decrease to 0.1%.

[0181] (2) Preparation of pelleting material;

[0182] After processing, the steel slag is mixed with metallurgical dust (i.e., a mixture of blast furnace ash and OG mixed dust in a mass ratio of 1:3.5) and used as pelletizing material. It is then divided into three parts, labeled as material A, material B, and material C. 0.75% of desulfurization ash is added to material B, and 2.5% of desulfurization ash is added to material C for later use.

[0183] (3) Layered ball formation;

[0184] The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 7mm. Then material B is added and pressed to form an intermediate layer with a thickness of 3.5mm. Finally, material C is added and pressed to form an outer layer with a thickness of 3.5mm.

[0185] (4) Carbonation and solidification treatment of green pellets;

[0186] Sintering flue gas or rotary hearth furnace flue gas is introduced into the green pellets for carbonation and solidification treatment. The introduced industrial waste gas flow rate is 80,000 m / s. 3 The process was carried out at a temperature of 190℃, a CO2 concentration of 4%, a water content of 4%, and a treatment time of 12 hours to obtain cold-consolidated pellets.

[0187] The obtained cold-consolidated pellets are dried and calcined to produce metallized finished pellets. The specific operation is as follows:

[0188] Dry at 200℃ for 5 minutes, then calcine at 1250℃ for 25 minutes to form pellets.

[0189] The performance of the obtained cold-consolidated pellets and the calcined metallized pellets was tested, and the test results are shown in Table 1.

[0190] Table 1. Performance test results of the pellets obtained in each embodiment and comparative example.

[0191]

[0192]

[0193] Furthermore, taking the pellets with the composition of Example 1-1 and Comparative Example 1-1 as examples, we further investigated the strength changes of the cold-consolidated pellets under different carbonation times.

[0194] Green pellets with the composition of Example 1-1 were subjected to industrial flue gas treatment for 0h, 2h, 4h, 6h, 8h, 10h, and 12h respectively, resulting in carbonated cold-bonded pellets. At the same time, green pellets with the composition of Comparative Example 1-1 were subjected to industrial flue gas treatment for 0h, 2h, 4h, 6h, 8h, 10h, and 12h respectively, resulting in carbonated cold-bonded pellets.

[0195] The cold-consolidated pellets with different compositions and different carbonation times were tested, and the results are shown in Table 2.

[0196] Table 2 Strength of cold-consolidated pellets under different carbonation times

[0197] Example 1-1 20.9 120.3 275.8 341.3 356.7 359.3 361.8 Comparative Example 1-1 20.7 140.6 196.6 200.3 206.3 209.3 210.5

[0198] As shown in Table 2, in Comparative Example 1-1 without the addition of a retarder, the reaction proceeded rapidly within 0-4 hours. Further extending the carbonation time did not significantly improve the compressive strength of the pellets, indicating that the carbonation reaction was essentially complete. This is mainly because the pellet carbonation reaction is a stepwise process from the outer layer to the inner layer. The high concentration of CO2 in the industrial flue gas can quickly react with the outer dicalcium silicate, tricalcium silicate, and other substances to form calcium carbonate precipitates, filling the pores between the raw materials. This results in a denser and more compact outer shell, leading to a certain degree of strength improvement. The main reason for this is the densification of the outer pellets. However, further extending the flue gas injection time makes it difficult for CO2 to penetrate from the dense outer shell into the pellet interior, resulting in an uneven and incomplete carbonation reaction. This reduces the amount of solidified material in the pellets, creating a state of high outer layer strength and low inner layer strength, ultimately reducing the overall strength of the pellets.

[0199] In Example 1-1, by adding retarder materials such as desulfurization ash and desulfurization gypsum to the pellet raw materials and distributing them appropriately, the problem of uneven and insufficient carbonation of cold-consolidated pellets using industrial waste gas can be effectively solved, thereby further improving the strength of the obtained pellets. Analysis shows that desulfurization ash and desulfurization gypsum contain components such as CaSO3 and CaSO4, which react with water to form anhydrite, a hydration product. The formation of anhydrite consumes some calcium ions (CaSO3, CaSO4, CaSO4) in the water. 2+This reduces the concentration of free calcium ions, thereby slowing down the hydration rate of tricalcium silicate and dicalcium silicate, and delaying the carbonation reaction rate. In this embodiment, the outer layer uses 2-4 times more retarder than the middle layer, while the inner layer uses no retarder. Under this system, the carbonation reaction rates of the outer, middle, and inner layers of the pellet can be kept consistent, ultimately achieving uniformity and completeness in the pellet carbonation reaction, thus significantly improving the pellet strength.

[0200] More specifically, although exemplary embodiments of the invention have been described herein, the invention is not limited to these embodiments, but includes any and all embodiments modified, omitted, such as combinations between various embodiments, adaptive changes, and / or substitutions, as would be apparent to those skilled in the art from the foregoing detailed description. The limitations in the claims are to be interpreted broadly as used in the language of the claims and are not limited to the examples described in the foregoing detailed description or during the implementation of this application, which should be considered non-exclusive. Any step listed in any method or process claim may be performed in any order and is not limited to the order set forth in the claims. Therefore, the scope of the invention should be determined solely by the appended claims and their legal equivalents, and not by the description and examples given above.

[0201] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail. When a rate, pressure, temperature, time, or other value or parameter is expressed as a range, preferred range, or a range defined by a series of upper and lower preferred values, this shall be understood to specifically disclose all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is disclosed individually. For example, the range 1-50 should be understood to include any number, combination of numbers, or subrange selected from 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, as well as all decimal values ​​between the integers mentioned above, such as 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, and 1.9. Regarding subranges, specifically consider "nested subranges" extending from any endpoint of the range. For example, nested sub-ranges of the exemplary range 1-50 may include 1-10, 1-20, 1-30 and 1-40 in one direction, or 50-40, 50-30, 50-20 and 50-10 in another direction.

Claims

1. A retarded setting cold bonded pellet for improving pellet strength, characterized by: The cold-bonded pellets comprise a three-layer structure, consisting of an inner layer (1), a middle layer (2), and an outer layer (3) from the inside out. All three layers of the pellet structure contain steel slag and metallurgical dust. The middle layer (2) and the outer layer (3) contain additional retarder. The mass ratio of steel slag to metallurgical dust is 1:(10~20). No retarder is added to the inner layer (1). The amount of retarder added to the middle layer (2) is 0.5%~1.0% of the total mass of the middle layer (2). The amount of retarder added to the outer layer (3) is 1.0%~4.0% of the total mass of the outer layer (3). The mass percentage of the retarder in the middle layer (2) is less than that in the outer layer (3).

2. The retarded cold-consolidated pellet for improving pellet strength according to claim 1, characterized in that: The mass ratio of the retarder in the outer layer (3) is 2 to 4 times that of the retarder in the middle layer (2). The retarder is desulfurized ash or desulfurized gypsum.

3. The retarded cold-consolidated pellet for improving pellet strength according to claim 1, characterized in that: The inner layer (1) of the pellet has a diameter of 6-8 mm, and the thickness of the middle layer (2) and the outer layer (3) are both 3-4 mm.

4. A retarded cold-consolidated pellet for improving pellet strength according to any one of claims 1-3, characterized in that: The three-layer pellet structure also includes alkali-containing dust, which is pre-filled in the pores (401) on the surface of the steel slag (4).

5. A method for preparing retarded cold-consolidated pellets as described in any one of claims 1-4, characterized in that: Includes the following steps: Step 1: Pre-treatment of steel slag to create porous steel slag; Step 2: Preparation of pelleting material; Prepare the inner layer pelletizing material, the middle layer pelletizing material and the outer layer pelletizing material respectively, which correspond to material A, material B and material C respectively, for later use; Step 3: Layered ball formation: The inner layer is made by mixing material A with water and pressing it into pellets with a diameter of 6-8 mm. Then, material B is added and pressed to form an intermediate layer with a thickness of 3-4 mm (2). Finally, material C is added and pressed to form an outer layer with a thickness of 3-4 mm (3). Step 4: Introduce industrial waste gas to carbonate and solidify the green pellets, resulting in cold-solidified pellets.

6. The method for preparing retarded cold-consolidated pellets with improved pellet strength according to claim 5, characterized in that: In step one, the steel slag is ground to a particle size of -0.149mm with a mass percentage content of ≥95%, and then the steel slag is immersed in an acidic solution for pickling to control the free CaO content to decrease to 0.1%-0.3%; the metallurgical dust in the pelletizing material is blast furnace ash or OG mixed dust, and the metallurgical dust has a particle size of -0.074mm with a mass percentage content of ≥80%.

7. The method for preparing retarded cold-consolidated pellets with improved pellet strength according to claim 6, characterized in that: The acidic solution is a mixture of formic acid and acetic acid, wherein the molar ratio of formic acid to acetic acid is 1:(0.5~2); the metallurgical dust is a combination of blast furnace ash and OG mixed dust, wherein the mass ratio of blast furnace ash to OG mixed dust is 1:(3~4).

8. The method for preparing retarded cold-consolidated pellets with improved pellet strength according to claim 5, characterized in that: When porous steel slag is filled with alkali-containing dust, the alkali-containing dust is sintering machine head ash, which is ground to a particle size of -13μm and has a mass percentage content of ≥95%. The mass ratio of alkali-containing dust to steel slag is (0.04~0.10):1, and the mixing time is 10~30min.

9. An application of a retarded cold-consolidated pellet as described in any one of claims 1-4, characterized in that: The slow-setting cold-consolidated pellets were placed in a rotary hearth furnace for drying and calcination. The drying temperature was 150-250℃ and the drying time was 5-10 min. The calcination temperature was 1250-1350℃ and the calcination time was 15-25 min.

Images