Method for value-added utilization of iron-containing fine impurities and application

Abstract

The invention discloses a value-added utilization method and application of iron-containing fine impurities, and relates to the technical field of ferrous metallurgy. The method comprises the following steps: taking 10-30% by mass of iron-containing fine miscellaneous materials and 70-90% by mass of mixed coal powder as raw materials, additionally adding a composite additive which accounts for 13-27% of the total mass of the raw materials, and mixing, briquetting and carbonizing to obtain iron coke; wherein the composite additive is composed of asphalt and aluminum dihydrogen phosphate. The application is as follows: the iron coke obtained by adopting the method for value-added utilization of the iron-containing fine miscellaneous materials is used for blast furnace ironmaking, so that the coke ratio can be reduced, the smelting efficiency and the resource utilization rate can be improved, the production cost can be reduced, and the effects of energy conservation and emission reduction are achieved.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy technology, specifically to a method and application for the value-added utilization of iron-containing fine impurities. Background Technology

[0002] Iron coke, as a carbon-iron composite furnace charge, is a highly reactive coke produced by mixing iron-containing materials and coking coal. During carbonization, iron oxides in the raw materials are reduced to fine metallic iron particles. Fe (Fe) plays a moderate catalytic role in the gasification and dissolution reaction of the coke, thus giving the composite iron coke high reactivity. The iron-containing fine materials used can include blast furnace ash, converter dust, zinc-containing dust, sintering return ore, metal slag, ultrafine iron ore powder, and low-grade iron ore powder, etc. Therefore, iron coke technology can improve the efficiency of waste resource recycling. When iron coke is used in blast furnaces, it undergoes a gasification reaction preferentially over coke, absorbing a large amount of heat in a short time. This effectively reduces the temperature of the heat reserve zone, improves smelting efficiency, reduces coke consumption, lowers the coke ratio, and reduces CO2 emissions. Furthermore, with the development of the steel industry, global high-quality iron ore resources are gradually decreasing, and iron ore prices are rising year by year, making abundant iron-containing fine materials increasingly attractive.

[0003] Currently, iron-containing fine aggregates are mainly used in sintering and recycling sintering (such as sintered return ore, metal slag, etc.) and metallization pellet preparation (such as blast furnace ash, ultrafine iron ore powder, and low-grade iron ore). However, most iron-containing fine aggregates have extremely fine particle sizes, low iron content, complex compositions, poor pelletizing properties, and are prone to dust generation due to their fine particles. Furthermore, the sintering bed has poor permeability, affecting sintering efficiency. Therefore, they are difficult to widely utilize in traditional blast furnace ironmaking. If iron-containing fine aggregates could be used in the preparation of iron coke, it could effectively improve the utilization rate of ultrafine iron concentrate and alleviate the shortage of coking coal resources. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a method and application for the value-added utilization of iron-containing fine impurities. This solves the problem of low utilization rate of iron-containing fine impurities and provides a method for preparing high-strength and highly reactive iron coke from iron-containing fine impurities. The resulting iron coke is suitable for blast furnace ironmaking, can reduce the coke ratio, improve smelting efficiency and resource utilization, reduce production costs, and has the effect of energy conservation and emission reduction.

[0005] A first aspect of the present invention provides a method for value-added utilization of iron-containing fine impurities, comprising: Using 10% to 30% by mass of iron-containing fine impurities and 70% to 90% by mass of blended coal powder as raw materials, and additionally adding 13% to 27% by mass of the total raw materials as composite additives, the mixture is mixed, briquetteted and carbonized to obtain iron coke; The composite additive is composed of asphalt and aluminum dihydrogen phosphate.

[0006] Furthermore, the iron-containing fine materials include zinc-containing dust, sintered return ore, metal slag and / or ultrafine iron ore powder, and the total iron content in the iron-containing fine materials is 20wt%~65wt%.

[0007] Furthermore, the blended pulverized coal is composed of the following coal types in parts by mass: 1 / 3 coking coal 30-45 parts; 0-10 parts of prime coking coal; 5-20 parts lean coal; 0-10 parts of anthracite.

[0008] Furthermore, the asphalt accounts for 3% to 7% of the total mass of the raw materials, and the aluminum dihydrogen phosphate accounts for 10% to 20% of the total mass of the raw materials.

[0009] Furthermore, the asphalt has a softening point of 52℃~68℃, an ash content of 0.22wt%~0.28wt%, and a coking value of 52%~56%.

[0010] Furthermore, the method also includes: Drying: The iron-containing fine impurities and coal are dried separately. The coal is crushed and screened to make the particle size of the blended coal powder less than 4 mm; the iron-containing fine impurities are screened to make the particle size less than 0.15 mm.

[0011] Further, the pressing block includes: The mixed materials are preheated at 200℃~300℃, and then formed by rollers under a pressure of 5MPa~10MPa.

[0012] Further, the carbonization includes: The first stage of carbonization involves raising the temperature from room temperature to 530℃~600℃ at a rate of 3℃ / min~5℃ / min. The second stage of carbonization involves raising the temperature from 530℃~600℃ to 900℃~1100℃ at a rate of 5℃ / min~7℃ / min, and then maintaining the temperature for 3~5 hours.

[0013] Furthermore, the iron coke prepared using asphalt and aluminum dihydrogen phosphate as composite additives exhibits superior compressive strength, drum strength, reactivity CRI, and post-reaction strength CRS compared to iron coke prepared using only asphalt as an additive.

[0014] In a second aspect, the present invention provides an application of iron coke, wherein the iron coke obtained by the above-mentioned method for value-added utilization of iron-containing fine impurities is used in blast furnace ironmaking.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects: The method for value-added utilization of iron-containing fine impurities provided by this invention produces iron coke with superior performance compared to traditional iron coke. It is suitable for blast furnaces, can reduce the coke ratio, improve smelting efficiency and resource utilization, lower production costs, and has energy-saving and emission-reduction effects. It has significant application prospects and economic benefits in the iron and steel metallurgical industry, providing a feasible path for the low-carbon transformation of the iron and steel industry. Detailed Implementation

[0016] To better understand the above technical solutions, the technical solutions of the embodiments of this application will be described in detail below through specific examples. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of the embodiments of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.

[0017] A first aspect of the present invention provides a method for value-added utilization of iron-containing fine impurities, comprising: Iron coke is obtained by mixing, briquetting, and carbonizing 10% to 30% by weight of iron-containing fine impurities and 70% to 90% by weight of blended coal powder, with an additional 13% to 27% by weight of composite additives. The composite additive consists of asphalt and aluminum dihydrogen phosphate.

[0018] This invention provides a method for the value-added utilization of iron-containing fine waste materials. By using these difficult-to-use iron-containing fine waste materials in the preparation of blast furnace coke, and combining them with appropriate amounts of pulverized coal, pitch, and aluminum dihydrogen phosphate, a highly reactive blast furnace coke with strength meeting the requirements for furnace loading is successfully produced. This achieves the rational utilization of this type of waste resource and effectively improves the utilization rate of waste resources in my country. The addition of pitch helps improve the cold strength of the blast furnace coke, ensuring that it is not easily broken or pulverized during transportation and charging. Aluminum dihydrogen phosphate significantly enhances the hot strength of the blast furnace coke, allowing it to maintain good structural integrity during blast furnace ironmaking, reducing powder generation, and thus ensuring the permeability of the blast furnace charge. Furthermore, aluminum dihydrogen phosphate can react with harmful components such as alkali metals (e.g., K, Na) introduced from the raw materials to generate stable phosphates, reducing their erosion and damage to the blast furnace lining and helping to extend the service life of the blast furnace. The prepared blast furnace coke is superior to traditional blast furnace coke in terms of strength and metallurgical properties, making it suitable for blast furnace smelting.

[0019] In some embodiments, the iron-containing fine impurities include zinc-containing dust, sintered return ore, metal slag and / or ultrafine iron ore powder, and the total iron content in the iron-containing fine impurities is 20wt%~65wt%.

[0020] Specifically, the iron-containing fine impurities have extremely fine particle sizes, with most materials having a particle size of less than 0.1 mm, even reaching the micrometer level. If directly added to the sintering mixture, it will severely deteriorate the permeability of the material bed, leading to a decrease in sintering speed, an increase in energy consumption, and a reduction in output and quality. In addition, once the harmful elements Zn and Pb enter the blast furnace, they will form a vicious cycle of accumulation, ultimately leading to blast furnace nodules and lining damage, causing huge economic losses.

[0021] In some embodiments, the pulverized coal is composed of the following coal types in parts by mass: 30-45 parts of 1 / 3 coking coal, 0-10 parts of prime coking coal, 5-20 parts of lean coal, and 0-10 parts of anthracite.

[0022] Specifically, in the process of preparing ferrocoke using iron-containing fine impurities, prime coking coal provides high-quality plastic mass, which acts as a binder phase to firmly bind inert components (such as iron-containing materials and anthracite) together, forming a solid framework. While 1 / 3 coking coal typically has a higher volatile matter content than prime coking coal, it can still produce sufficient plastic mass to replace prime coking coal, reducing raw material costs. The addition of lean coal can increase the viscosity of the plastic mass, increase the toughness of the semi-coke stage, and reduce internal and external cracks caused by uneven shrinkage, thereby improving the strength of ferrocoke. Anthracite is a non-caking coal; it does not soften or produce plastic mass during carbonization, and its dispersion within the plastic mass helps improve mechanical strength. Utilizing non-coking coals such as weakly caking coal and non-caking coal is not only inexpensive but also greatly improves the availability of raw materials and the comprehensive utilization of waste.

[0023] In some embodiments, in the composite additive, asphalt accounts for 3% to 7% of the total mass of the raw materials, and aluminum dihydrogen phosphate accounts for 10% to 20% of the total mass of the raw materials.

[0024] Specifically, bitumen primarily acts as a "process binder," with a 3% bitumen content being the minimum effective amount to ensure the initial strength of the green pellets. Once the bitumen content reaches 7%, the initial strength of the green pellets no longer increases. Aluminum dihydrogen phosphate primarily acts as a "final strength binder," providing final strength after carbonization and at high temperatures. Insufficient addition of aluminum dihydrogen phosphate will result in insufficient strength of the iron coke, while excessive addition will cause its binder phase to occupy the internal pores of the iron coke, reducing its reactivity.

[0025] In some embodiments, unless otherwise specified, the asphalt in the embodiments and comparative examples of the present invention has a softening point of 52°C to 68°C, an ash content of 0.22wt% to 0.28wt%, and a coking value of 52% to 56%.

[0026] Specifically, the above-mentioned asphalt performance indicators include low operating temperature, reduced energy consumption, reduced blast furnace slag content, increased fixed carbon content in iron coke, and high strength and reactivity of iron coke. After cold pressing, the asphalt with a medium softening point will solidify rapidly, giving the green balls cold strength.

[0027] In some embodiments, the method for value-added utilization of iron-containing fine impurities further includes: Drying involves drying iron-containing fine materials and coal separately; drying removes excess moisture from the raw materials, improves mixing uniformity, and reduces energy consumption.

[0028] Crushing and screening processes are used to crush the coal, ensuring the particle size of the pulverized coal is less than 4mm. Screening further reduces the particle size of iron-containing fine impurities to less than 0.15mm. This refined pulverized coal ensures a uniform distribution of the plastic mass, effectively coating the iron-containing materials, strengthening the interparticle bonding force, and directly enhancing the strength of the coke. Controlling the particle size guarantees consistent product quality across batches.

[0029] In some embodiments, the briquetting process includes: preheating the mixed material at 200°C to 300°C, and then forming it by rollers under a pressure of 5MPa to 10MPa.

[0030] Specifically, the optimized briquetting parameters described above enable the green pellets to simultaneously achieve high density and high initial strength, ultimately resulting in iron coke with a dense structure, uniform strength, and good pore structure. Too low a pressure cannot guarantee the strength of the green pellets, while too high a pressure leads to the destruction of the pore structure and reduces the reactivity of the iron coke.

[0031] In some embodiments, carbonization includes: The first stage of carbonization involves raising the temperature from room temperature to 530℃~600℃ at a rate of 3℃ / min~5℃ / min. The second stage of carbonization involves raising the temperature from 530℃~600℃ to 900℃~1100℃ at a rate of 5℃ / min~7℃ / min, and then maintaining the temperature for 3~5 hours.

[0032] Specifically, a two-stage carbonization process is adopted, and the reaction path can be precisely optimized by controlling key parameters (such as temperature, heating rate, atmosphere, and residence time). On the one hand, the two-stage carbonization process can efficiently remove volatile harmful elements such as Zn and Pb from iron-containing fine impurities, cutting off their enrichment and circulation in the process flow from the source; on the other hand, by regulating the pyrolysis process, it can promote the formation of high-strength iron coke, achieving the simultaneous goal of removing harmful elements and improving the quality of iron coke.

[0033] In summary, the iron coke obtained by the method of value-added utilization of iron-containing fine impurities in the embodiments of the present invention has a compressive strength ≥2500N, drum strength ≥70%, reactivity CRI ≥60%, and post-reaction strength CRS ≥50%. Moreover, the iron coke prepared by using asphalt and aluminum dihydrogen phosphate as composite additives has better compressive strength, drum strength, reactivity CRI, and post-reaction strength CRS than the iron coke prepared by using asphalt as an additive alone.

[0034] In a second aspect, this invention provides an application of iron coke. Iron coke obtained by the above-mentioned method of value-added utilization of iron-containing fine impurities can be used in blast furnace ironmaking, which can effectively reduce the temperature of the heat reserve zone, reduce the coke ratio, and improve smelting efficiency. It has significant energy-saving and emission-reduction effects and provides a feasible path for the low-carbon transformation of the steel industry.

[0035] The technical solution of the present invention will be further described below through embodiments and comparative examples; wherein, the iron-containing fine impurities and blended coal powder used in the embodiments and comparative examples are shown in Table 1 and Table 2.

[0036] Table 1. Types and main chemical composition of iron-containing fine impurities (wt%)

[0037] Table 2 Industrial analysis of pulverized coal (mass fraction, %)

[0038] FC: Fixed Carbon, A: Ash, V: Volatile Matter, M: Moisture, ad: Air-dried Basis Example 1 (a) Raw material preparation The raw materials, by weight percentage, are: 30% ultrafine iron ore powder and 70% blended coal powder; among which, the blended coal powder specifically consists of 45% 1 / 3 coking coal, 5% prime coking coal, 15% lean coal, and 5% anthracite.

[0039] External additives (compound additives): 3% asphalt by the total mass of raw materials (total mass of ultrafine iron ore powder and blended coal powder) and 10% aluminum dihydrogen phosphate by the total mass of raw materials (total mass of ultrafine iron ore powder and blended coal powder).

[0040] (II) Preparation process Includes the following steps: S1 Raw material drying: Dry the ultrafine iron ore powder and coal at a constant temperature of 105℃ for 5 hours; S2 Crushing and Screening: The coal is crushed to collect coal powder with a particle size of less than 4mm; the ultrafine iron ore powder is screened to below 0.15mm. S3 Mixing: Add ultrafine iron ore powder, blended coal powder and composite additives to the mixing equipment according to the predetermined ratio, stir and mix thoroughly for no less than 10 minutes to ensure uniform distribution of raw materials; S4 Briquetting: The mixed material is preheated in a muffle furnace at 240°C for 5 minutes, and then fed into a roller forming machine to be formed into oval green balls under a pressure of 6MPa. S5 carbonization: The formed green pellets are placed in a muffle furnace for carbonization. A two-stage carbonization process is adopted. In the first stage, the temperature is increased from room temperature to 550℃ at a rate of 3℃ / min. In the second stage, the temperature is increased from 550℃ to 1000℃ at a rate of 5℃ / min. The temperature is kept constant at 1000℃ for 4 hours. After carbonization, the product is cooled in an inert atmosphere to obtain the final iron coke product. The metallurgical properties are shown in Table 3.

[0041] Example 2 (a) Raw material preparation The raw materials, by weight percentage, are: 30% sintered return ore and 70% blended coal powder; among which, the blended coal powder specifically consists of 45% 1 / 3 coking coal, 5% prime coking coal, 15% lean coal, and 5% anthracite.

[0042] External additives (compound additives): 3% asphalt by weight of raw materials and 10% aluminum dihydrogen phosphate by weight of raw materials.

[0043] (II) Preparation process Includes the following steps: S1 Raw Material Drying: The sintered return ore and coal are dried at a constant temperature of 105℃ for 5 hours; S2 Crushing and Screening: The coal is crushed to collect coal powder with a particle size of less than 4mm; the sintered return ore is screened to below 0.15mm; S3 Mixing: Add sintered return ore, pulverized coal and composite additives to the mixing equipment in a predetermined ratio, stir and mix thoroughly for no less than 10 minutes to ensure uniform distribution of raw materials; S4 Briquetting: The mixed material is preheated in a muffle furnace at 240°C for 5 minutes, and then fed into a roller forming machine to be formed into oval green balls under a pressure of 6MPa. S5 carbonization: The formed green pellets are placed in a muffle furnace for carbonization. A two-stage carbonization process is adopted. In the first stage, the temperature is increased from room temperature to 550℃ at a rate of 3℃ / min. In the second stage, the temperature is increased from 550℃ to 1000℃ at a rate of 5℃ / min. The temperature is kept constant at 1000℃ for 4 hours. After carbonization, the product is cooled in an inert atmosphere to obtain the final iron coke product. The metallurgical properties are shown in Table 3.

[0044] Example 3 (a) Raw material preparation The raw materials, by weight percentage, are: 15% steel slag and 85% blended coal powder; among which, the blended coal powder specifically consists of 45% 1 / 3 coking coal, 10% prime coking coal, 20% lean coal, and 10% anthracite.

[0045] External additives (compound additives): 3% asphalt by weight of raw materials and 10% aluminum dihydrogen phosphate by weight of raw materials.

[0046] (II) Preparation process Includes the following steps: S1 Raw Material Drying: Dry steel slag and coal at a constant temperature of 105℃ for 5 hours; S2 Crushing and Screening: The coal is crushed to collect coal powder with a particle size of less than 4 mm; the steel slag with a particle size of less than 0.15 mm is collected by screening. S3 Mixing: Add steel slag, pulverized coal and composite additives to the mixing equipment according to the predetermined ratio, stir and mix thoroughly for no less than 10 minutes to ensure uniform distribution of raw materials; S4 Briquetting: The mixed material is preheated in a muffle furnace at 240°C for 5 minutes, and then fed into a roller forming machine to be formed into oval green balls under a pressure of 6MPa. S5 carbonization: The formed green pellets are placed in a muffle furnace for carbonization. A two-stage carbonization process is adopted. In the first stage, the temperature is increased from room temperature to 550℃ at a rate of 5℃ / min. In the second stage, the temperature is increased from 550℃ to 900℃ at a rate of 7℃ / min. The temperature is kept constant at 900℃ for 4 hours. After carbonization, the product is cooled in an inert atmosphere to obtain the final iron coke product. The metallurgical properties are shown in Table 3.

[0047] Example 4 (a) Raw material preparation The raw materials, by weight percentage, are: 25% zinc dust and 75% blended coal powder; specifically, the blended coal powder consists of 45% 1 / 3 coking coal, 10% prime coking coal, 10% lean coal, and 10% anthracite.

[0048] External additives (compound additives): 3% asphalt by weight of raw materials and 10% aluminum dihydrogen phosphate by weight of raw materials.

[0049] (II) Preparation process Includes the following steps: S1 Raw material drying: Dry zinc-containing dust and coal at a constant temperature of 105℃ for 5 hours; S2 Crushing and Screening: The coal is crushed to collect coal powder with a particle size of less than 4 mm; zinc-containing dust with a particle size of less than 0.15 mm is collected by screening. S3 Mixing: Add zinc dust, pulverized coal and composite additives to the mixing equipment in a predetermined ratio, stir and mix thoroughly for no less than 10 minutes to ensure uniform distribution of raw materials; S4 Briquetting: The mixed material is preheated in a muffle furnace at 240°C for 5 minutes, and then fed into a roller forming machine to be formed into oval green balls under a pressure of 8MPa. S5 carbonization: The formed green pellets are placed in a muffle furnace for carbonization. A two-stage carbonization process is adopted. In the first stage, the temperature is increased from room temperature to 550℃ at a rate of 3℃ / min. In the second stage, the temperature is increased from 550℃ to 1100℃ at a rate of 5℃ / min. The temperature is kept constant at 1100℃ for 4 hours. After carbonization, the product is cooled in an inert atmosphere to obtain the final iron coke product. The metallurgical properties are shown in Table 3.

[0050] Example 5 The difference between Example 5 and Example 1 is that the external additives are: asphalt accounting for 3% of the total mass of raw materials, and aluminum dihydrogen phosphate accounting for 15% of the total mass of raw materials.

[0051] Example 6 The difference between Example 6 and Example 1 is that the external additives are: asphalt accounting for 3% of the total mass of raw materials, and aluminum dihydrogen phosphate accounting for 20% of the total mass of raw materials.

[0052] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the external additives are: asphalt accounting for 3% of the total mass of raw materials and aluminum dihydrogen phosphate accounting for 0% of the total mass of raw materials.

[0053] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the external additives are: asphalt accounting for 3% of the total mass of raw materials and aluminum dihydrogen phosphate accounting for 5% of the total mass of raw materials.

[0054] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the external additives are: asphalt accounting for 3% of the total mass of raw materials and aluminum dihydrogen phosphate accounting for 25% of the total mass of raw materials.

[0055] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the external additive is asphalt accounting for 5% of the total mass of the raw materials.

[0056] Comparative Example 5 The difference between Comparative Example 5 and Example 2 is that the external additive is asphalt accounting for 5% of the total mass of the raw materials.

[0057] Comparative Example 6 The difference between Comparative Example 6 and Example 3 is that the external additive is asphalt accounting for 5% of the total mass of the raw materials.

[0058] Comparative Example 7 The difference between Comparative Example 7 and Example 4 is that the external additive is asphalt, which accounts for 5% of the total mass of the raw materials.

[0059] Comparative Example 8 The difference between Comparative Example 8 and Example 1 is that the ultrafine iron ore powder is replaced with ordinary iron concentrate; and the external additive is asphalt accounting for 5% of the total mass of the raw materials.

[0060] Table 3. Metallurgical properties of iron coke prepared in different embodiments and comparative examples

[0061] The results of Examples 1-4 show that the key properties of the prepared iron coke, such as compressive strength (≥2500N), drum strength (≥70%), reactivity (CRI≥60%), and post-reaction strength (CRS≥50%), all meet metallurgical requirements. Compared with Comparative Examples 4-7 using traditional pitch as an additive, the iron coke using aluminum dihydrogen phosphate additive is significantly superior to the traditional iron coke of Comparative Examples 4-7 in both strength and metallurgical performance. The reason for this is that aluminum dihydrogen phosphate undergoes decomposition and condensation reactions at high temperatures, generating a glassy / ceramic network structure of aluminum metaphosphate. This catalyzes the cross-linking and carbonization reactions of organic matter, allowing it to be converted into coke more smoothly, increasing its fixed carbon content, reducing the explosive adhesion caused by violent volatilization, and improving the hot strength of the iron coke. Furthermore, the aluminum metaphosphate ceramic phase in blast furnace ironmaking can maintain high strength, maintain the pore structure of the iron coke at high temperatures, thereby maintaining the gas reaction rate, increasing the reactivity of the iron coke, and thus improving its metallurgical performance.

[0062] As shown in Examples 1-4 and Comparative Example 8, most iron-containing fine impurities exhibit higher metallurgical properties than traditional iron-containing coke. This is likely because the iron-containing fine impurities are mostly micron-sized fine powders, uniformly dispersed within the carbon matrix of the coke, forming numerous iron-carbon reaction interfaces and enhancing the reactivity of the iron-containing coke. Furthermore, the reduction of fine iron oxides leads to their migration and aggregation, forming a metallic iron skeleton, thus increasing the strength of the iron-containing coke. In Example 4, due to significant differences in the composition of the raw materials, its reactivity was lower than that of the traditional iron-containing coke in Comparative Example 8.

[0063] Analysis of Comparative Example 1 shows that when the aluminum dihydrogen phosphate content in the composite additive is 0%, the drum strength of the iron coke is 62%, and the post-reaction strength (CRS) of the iron coke is 41.2%, which does not meet the strength requirements for actual iron coke production.

[0064] Analysis of Comparative Example 2 and Example 1 shows that a certain amount of aluminum dihydrogen phosphate needs to be added to significantly improve the strength of iron coke; conversely, if the amount added is too low, the strengthening effect is not obvious, resulting in poor product performance. When the amount added is too low, the generated aluminum metaphosphate is insufficient to construct a complete network structure, and under the impact and friction of the drum test, cracks can easily originate and propagate from these weak points.

[0065] As shown in Examples 5-6 and Example 1, the reinforcing effect of aluminum dihydrogen phosphate has certain limitations. As the aluminum dihydrogen phosphate content continues to increase, the compressive strength and post-reaction strength of the iron coke continue to rise, while its reactivity gradually decreases. The reason for this is that the excess aluminum dihydrogen phosphate forms a binder phase that fills the pores between the iron coke particles, making the overall structure of the iron coke more compact. This increases the strength of the iron coke but reduces its reactivity. As shown in Comparative Example 3, when the aluminum dihydrogen phosphate content is 25%, the reactivity of the iron coke does not meet production requirements. Therefore, in a suitable external compound additive, the amount of asphalt added is 3% of the total mass of the raw materials, and the amount of aluminum dihydrogen phosphate added is 10%-20% of the total mass of the raw materials; preferably, in the external compound additive, the amount of asphalt added is 3% of the total mass of the raw materials, and the amount of aluminum dihydrogen phosphate added is 10% of the total mass of the raw materials.

[0066] It will be readily understood by those skilled in the art that the above-described advantageous methods can be freely combined and superimposed without conflict. The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A method for value-added utilization of iron-containing fine impurities, characterized in that, include: Using 10% to 30% by mass of iron-containing fine impurities and 70% to 90% by mass of blended coal powder as raw materials, and additionally adding 13% to 27% by mass of the total raw materials as composite additives, the mixture is mixed, briquetteted and carbonized to obtain iron coke; The composite additive is composed of asphalt and aluminum dihydrogen phosphate.

2. The method for value-added utilization of iron-containing fine waste materials according to claim 1, characterized in that, The iron-containing fine materials include zinc dust, sintered return ore, metal slag and / or ultrafine iron ore powder, and the total iron content in the iron-containing fine materials is 20wt%~65wt%.

3. The method for value-added utilization of iron-containing fine waste materials according to claim 1, characterized in that, The blended pulverized coal is composed of the following coal types in parts by mass: 1 / 3 coking coal 30-45 parts; 0-10 parts of prime coking coal; 5-20 parts lean coal; 0-10 parts of anthracite.

4. The method for value-added utilization of iron-containing fine waste materials according to claim 1, characterized in that, In the composite additive, the asphalt accounts for 3% to 7% of the total mass of the raw materials, and the aluminum dihydrogen phosphate accounts for 10% to 20% of the total mass of the raw materials.

5. The method for value-added utilization of iron-containing fine impurities according to claim 1 or 4, characterized in that, The asphalt has a softening point of 52℃~68℃, an ash content of 0.22wt%~0.28wt%, and a coking value of 52%~56%.

6. The method for value-added utilization of iron-containing fine waste materials according to claim 1, characterized in that, The method further includes: Drying: The iron-containing fine impurities and coal are dried separately. The coal is crushed and screened to make the particle size of the blended coal powder less than 4 mm; the iron-containing fine impurities are screened to make the particle size less than 0.15 mm.

7. The method for value-added utilization of iron-containing fine waste materials according to claim 1, characterized in that, The pressing block includes: The mixed materials are preheated at 200℃~300℃, and then formed by rollers under a pressure of 5MPa~10MPa.

8. The method for value-added utilization of iron-containing fine waste materials according to claim 1, characterized in that, The carbonization includes: The first stage of carbonization involves raising the temperature from room temperature to 530℃~600℃ at a rate of 3℃ / min~5℃ / min. The second stage of carbonization involves raising the temperature from 530℃~600℃ to 900℃~1100℃ at a rate of 5℃ / min~7℃ / min, and then maintaining the temperature for 3~5 hours.

9. The method for value-added utilization of iron-containing fine waste materials according to claim 1, characterized in that, Iron coke prepared using asphalt and aluminum dihydrogen phosphate as composite additives exhibits superior compressive strength, drum strength, reactivity (CRI), and post-reaction strength (CRS) compared to iron coke prepared using only asphalt as an additive.

10. An application of iron coke, characterized in that, The iron coke obtained by the method of value-added utilization of iron-containing fine impurities as described in any one of claims 1-9 is used for blast furnace ironmaking.

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