A method for strengthening sulphuric acid sludge oxidized pellets

Abstract

This invention discloses a method for strengthening sulfuric acid slag oxidation pellets, comprising the following steps: S1, mixing magnetite concentrate powder with a binder to obtain a first mixed ore; mixing magnetite concentrate powder, sulfuric acid slag, and a binder to obtain a second mixed ore; and mixing magnetite concentrate powder, sulfuric acid slag, and a binder to obtain a third mixed ore; S2, manufacturing a first pellet from the first mixed ore in a disc pelletizer; adding the second mixed ore to the first pellet to manufacture a second pellet; and adding the third mixed ore to the second pellet to manufacture a third pellet; S3, drying, preheating, roasting, and cooling the third pellet to obtain sulfuric acid slag oxidation pellets. This invention adds sulfuric acid slag, a solid waste resource, to the pellet raw materials to prepare sulfuric acid slag oxidation pellets, improving the utilization rate of sulfuric acid slag and helping to alleviate the problems of land occupation and environmental pollution caused by sulfuric acid slag accumulation. For low-grade pellet ore, sulfuric acid slag oxidation pellets increase the TFe grade and improve the grade of blast furnace feed.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a method for strengthening the oxidation of sulfuric acid slag pellets. Background Technology

[0002] Sulfuric acid slag is the roasting residue from the sulfuric acid production process using pyrite. It is an inevitable byproduct of acid production plants. Currently, large quantities of sulfuric acid slag exist throughout China, and this abundant secondary mineral resource has not been fully and effectively utilized. This not only occupies land resources but also poses a risk of environmental pollution. Sulfuric acid slag is mainly composed of calcium sulfate, iron oxides, and silicates. After a series of beneficiation and upgrading processes, the TFe grade can reach about 60%. The iron oxides are mainly magnetite and hematite, with Al2O3 at around 5%, and a relatively high S content, generally around 0.8%. It also has high levels of harmful elements such as K, Pb, and Zn. Sulfuric acid slag has an extremely fine particle size, with over 90% of particles <0.074mm. It has a rich microporous structure, strong water absorption, and an amorphous structure.

[0003] Sulfuric acid slag is mainly used in cement production, building materials, soil conditioners, and mine backfilling. In the metallurgical industry, it is commonly used as a high-powder raw material in the sintering process. Due to its high sulfur content, sintering can remove a significant amount of sulfur. However, its fine particle size and high water absorption can negatively impact the quality of the sintered ore, limiting its proportion in sintering and its processing capacity. The fine particle size and large specific surface area of ​​sulfuric acid slag allow it to act as a binder during pelletizing, leading to the development of a series of pellets incorporating sulfuric acid slag. The loose, porous structure of sulfuric acid slag determines its strong water absorption; the moisture content of green pellets made entirely from sulfuric acid slag can reach 23%, far exceeding the 7-9% of ordinary green pellets. This excessive moisture content hinders pellet drying; therefore, sulfuric acid slag is often added in small quantities to mixtures of iron concentrate and binders for pelletizing.

[0004] Because sulfuric acid slag has good crystal growth after roasting, less primary crystals are formed under high temperature conditions during the production of oxidized pellets, the bridging bond consolidation effect is weak, and the compressive strength of the pellets is low. Therefore, it is necessary to strengthen the oxidized pellets of sulfuric acid slag by improving the crystal defects of sulfuric acid slag and improving the pelletizing property of sulfuric acid slag. Common methods include increasing the high-pressure roller mill and pre-wetting sulfuric acid slag to improve the pelletizing property of the mixture.

[0005] For example, Chinese patent publication number CN101643842 discloses a method for directly producing oxidized pellets from sulfuric acid residue. The method includes pre-treating sulfuric acid residue by high-pressure roller mill, adding magnetite concentrate and organic composite bentonite, mixing well, pelletizing, drying and preheating, and oxidizing and roasting to obtain oxidized pellets.

[0006] For example, Chinese Patent Publication No. CN101597686 discloses a method for preparing sulfuric acid slag pellet raw material and a method for preparing green pellets, which includes the following steps: A) taking sulfuric acid slag and water for the first mixing to obtain a mixture, wherein the water content of the mixture is 1WT% to 13WT; B) subjecting the mixture to a bridging treatment; C) subjecting the bridging treatment mixture to a second mixing with water and other iron-containing raw materials to obtain pellet raw material.

[0007] In the above methods, high-pressure roller milling requires a large amount of electrical energy, increasing energy consumption in the production process. Under the same rolling conditions, as the moisture content of the iron material increases, the specific surface area and particle size distribution after rolling will deteriorate. Furthermore, when the moisture content of the iron material is too high, sticking to the rollers and a decrease in yield will occur. Although increasing the moisture content during grinding can improve the drop strength of the green balls, excessive moisture content will lead to severe phenomena of the mixture encapsulating the steel balls and the mixture sticking to the wall, making operation difficult.

[0008] In view of this, improvements should be made to the existing technology in order to solve the aforementioned problems. Summary of the Invention

[0009] The main objective of this invention is to provide a method for enhancing sulfuric acid slag oxidation pellets. By adding sulfuric acid slag, a solid waste resource, to the pellet raw materials to prepare sulfuric acid slag oxidation pellets, the utilization rate of sulfuric acid slag is improved, which helps to alleviate the problems of land occupation and environmental pollution caused by sulfuric acid slag accumulation. For low-grade pellet ore, sulfuric acid slag oxidation pellets improve the TFe grade and increase the grade of blast furnace feed.

[0010] According to one aspect of the present invention, a method for enhancing the oxidation of sulfuric acid slag pellets is provided, comprising the following steps: S1. Mix magnetite concentrate powder with a binder to obtain a first mixed ore; mix magnetite concentrate powder, sulfuric acid residue with a binder to obtain a second mixed ore; mix magnetite concentrate powder, sulfuric acid residue with a binder to obtain a third mixed ore, wherein the mass percentage of sulfuric acid residue in the second mixed ore is lower than the mass percentage of sulfuric acid residue in the third mixed ore. S2. The first mixed ore is made into the first pellet in the disc pelletizer, the second mixed ore is added to the first pellet to make the second pellet, and the third mixed ore is added to the second pellet to make the third pellet; S3. The third pellet is dried, preheated, roasted and cooled to obtain sulfuric acid slag oxidized pellets.

[0011] According to one embodiment of the present invention, the TFe grade in the magnetite concentrate is 53-56%, and the TFe grade in the sulfuric acid residue is 58-62%.

[0012] According to one embodiment of the present invention, the amount of sulfuric acid slag added to the second mixed ore is 2-6% by mass percentage, and the amount of sulfuric acid slag added to the third mixed ore is 6-10%.

[0013] According to one embodiment of the present invention, the binder comprises bentonite, and the amount of binder added is 1 to 3% by mass percentage.

[0014] According to one embodiment of the present invention, in step S2, the pelletizing time of the first pellet is 5-6 minutes, the pelletizing time of the second pellet is 8-12 minutes, and the pelletizing time of the third pellet is 5-6 minutes.

[0015] According to one embodiment of the present invention, the moisture content of the first pellet is controlled to be 7-8%, the moisture content of the second pellet is controlled to be 7-9%, and the moisture content of the third pellet is controlled to be 7-10%.

[0016] According to one embodiment of the present invention, the particle size of the first pellet is controlled to be 3-6 mm, the particle size of the second pellet is controlled to be 6-10 mm, and the particle size of the third pellet is controlled to be 10-13 mm.

[0017] According to one embodiment of the present invention, the magnetite concentrate is completely dried, and the proportion of particles <0.074mm is 90~98%.

[0018] According to one embodiment of the present invention, the sulfuric acid residue is completely dried, and the proportion of particles <0.074mm is 96~98%.

[0019] According to one embodiment of the present invention, the drying temperature range is 100~115℃, the preheating temperature range is 900℃~1000℃, and the calcination temperature range is 1230℃~1260℃.

[0020] In a method for strengthening sulfuric acid slag oxidation pellets according to an embodiment of the present invention, sulfuric acid slag, a solid waste resource, is added to the pellet raw materials to prepare sulfuric acid slag oxidation pellets, which improves the utilization rate of sulfuric acid slag and helps alleviate the problems of land occupation and environmental pollution caused by sulfuric acid slag accumulation. For low-grade pellet ore, sulfuric acid slag oxidation pellets improve the TFe grade and increase the grade of blast furnace feed. Using sulfuric acid slag as a solid waste resource reduces the cost of pellet raw materials. By preparing mother pellets with magnetite concentrate and a binder, the adverse effects of poor pelletizing performance caused by sulfuric acid slag are reduced. During the pelletizing process, the addition of sulfuric acid slag mixtures with different gradient proportions allows the green pellets to grow continuously, controlling the gradient distribution of moisture and density of the green pellets, solving the problem of large shrinkage after roasting of sulfuric acid slag pellets, and improving the mechanical strength of the green pellets and the compressive strength of the oxidation pellets. The sulfuric acid slag oxidation pellets obtained by this method have qualified compressive strength and good metallurgical properties, and have application and promotion value. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some implementation examples of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A process flow diagram of a method for enhancing the oxidation of sulfuric acid slag into pellets according to the present invention is shown; Figure 2 An embodiment of a method for strengthening the oxidation of sulfuric acid slag pellets according to the present invention is shown. Detailed Implementation

[0023] The following detailed description of the embodiments is intended to exemplify the principles of the present invention, but should not be construed as limiting the scope of the invention. The present invention can be implemented in many different forms and is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

[0024] These embodiments are provided to make this disclosure thorough and complete, and to fully express the scope of the invention to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​set forth in these embodiments should be interpreted as merely exemplary and not as limiting.

[0025] It should be noted that, in the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0026] It should also be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0027] All terms used in this invention have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0028] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0029] like Figure 1 As shown, the present invention provides a method for strengthening the oxidation of sulfuric acid residue into pellets, which includes the following steps: S1. Mix magnetite concentrate powder with a binder to obtain a first mixed ore; mix magnetite concentrate powder, sulfuric acid residue with a binder to obtain a second mixed ore; mix magnetite concentrate powder, sulfuric acid residue with a binder to obtain a third mixed ore, wherein the mass percentage of sulfuric acid residue in the second mixed ore is lower than the mass percentage of sulfuric acid residue in the third mixed ore. S2. The first mixed ore is made into the first pellet in the disc pelletizer, the second mixed ore is added to the first pellet to make the second pellet, and the third mixed ore is added to the second pellet to make the third pellet; S3. The third pellet is dried, preheated, roasted and cooled to obtain sulfuric acid slag oxidized pellets.

[0030] In some specific embodiments, the TFe grade in the magnetite concentrate is 53-56%, and the TFe grade in the sulfuric acid slag is 58-62%. A high TFe grade in the magnetite concentrate indicates a relatively low impurity content, thereby improving the purity of the product. This is crucial for subsequent smelting and processing steps, as it reduces the impact of impurities on product quality.

[0031] In some specific embodiments, the amount of sulfuric acid slag added to the second mixed ore is 2-6% by mass, and the amount added to the third mixed ore is 6-10%. By adding sulfuric acid slag mixtures in different gradient proportions to promote the continuous and stable growth of green pellets, this process not only requires precise control of the mixture ratio but also ensures that the sulfuric acid slag added in each layer is evenly distributed within the green pellets, forming a multi-layered, multi-gradient structure. The purpose of this is to optimize the internal pore structure and interparticle bonding force of the green pellets by adjusting the physicochemical properties of each layer of the mixture, such as particle size, density, and surface activity.

[0032] In some specific embodiments, the binder includes bentonite, with an addition amount of 1-3% by mass. Due to the unique physical and chemical properties of sulfuric acid slag, it is often difficult for it to form good spheres on its own, easily resulting in loose spheres, insufficient strength, and brittleness. Bentonite, as a natural mineral binder, has excellent water absorption, swelling, and binding properties, which can significantly improve the sphere-forming performance of the mixture. By mixing an appropriate amount of bentonite with magnetite concentrate, the viscosity of the mixture can be significantly improved, allowing the particles to bond more tightly together during the preparation of the mother spheres, forming dense, high-strength spheres. These mother spheres not only have better physical stability, resisting external impacts and abrasion, but also maintain their integrity during subsequent processing and transportation, reducing breakage and loss. Furthermore, the addition of bentonite helps regulate the moisture distribution and pore structure inside the mother spheres, allowing for better control of shrinkage and expansion during calcination or other treatments, reducing cracks and deformation caused by volume changes. This effect further improves the processing performance of the mother spheres and the quality stability of the final product.

[0033] like Figure 2 As shown, in some specific embodiments, in step S2, the pelletizing time for the first pellet is 5-6 minutes, the pelletizing time for the second pellet is 8-12 minutes, and the pelletizing time for the third pellet is 5-6 minutes. For example, the pelletizing time for the first pellet is 5 minutes, the pelletizing time for the second pellet is 10 minutes, and the pelletizing time for the third pellet is 5 minutes.

[0034] In some specific embodiments, the moisture content of the first pellet is controlled at 7-8%, the second pellet at 7-9%, and the third pellet at 7-10%. The moisture content of the first, second, and third pellets increases sequentially, exhibiting a gradient distribution. The appropriate amount of moisture is crucial for pellet formation, growth, and subsequent firing. By precisely controlling the moisture content at each stage, it is ensured that the pellets maintain appropriate moisture levels during growth, preventing both excessive dryness (leading to weak interparticle bonding) and excessive moisture (resulting in reduced mechanical strength). Simultaneously, the gradient distribution of moisture also helps to create more uniform shrinkage during firing, reducing stress concentration and cracking caused by localized moisture differences.

[0035] Appropriate particle size control helps to form a more ideal pore structure, improves the air permeability and calcination performance of the pellets, and facilitates uniform heating and effective sintering of the pellets in subsequent processing. Proper particle size control can also reduce the scrap rate caused by uneven particle size, excessively large or small particle size, thereby improving product qualification rate and economic benefits. In some specific embodiments, the particle size of the first pellet is controlled to be 3-6 mm, the particle size of the second pellet is controlled to be 6-10 mm, and the particle size of the third pellet is controlled to be 10-13 mm.

[0036] In some specific embodiments, the magnetite concentrate is completely dried, with 90-98% of particles <0.074mm, and the sulfuric acid slag is completely dried, with 96-98% of particles <0.074mm. Due to their smaller size and higher specific surface area, particles <0.074mm adhere better to each other, forming dense, high-strength pellets. This fine-grained mixed ore exhibits better pelletizing performance than coarse-grained particles, helping to reduce pellet breakage during production and transportation.

[0037] In some specific embodiments, the drying temperature range is 100~115℃, the preheating temperature range is 900℃~1000℃, and the calcination temperature range is 1230℃~1260℃.

[0038] In some specific embodiments, the mixed ore is a homogenized mineral powder. Homogenized mineral powder can eliminate compositional differences between different batches or from different sources, making the entire batch of mineral powder have similar chemical composition, particle size, and distribution characteristics. This uniformity helps ensure the stability and consistency of product quality in subsequent production processes.

[0039] The present application will be described below through specific embodiments and comparative examples.

[0040] Comparative Example 1 S1. Take completely dry magnetite concentrate powder with a TFe grade of 56% and a <0.074mm particle size of 96% and mix it with bentonite to obtain a homogeneous mineral powder. The mass percentage of magnetite concentrate is 98% and the mass percentage of bentonite is 2%.

[0041] S2. The mixed mineral powder from step S1 is pelletized in a disc pelletizer for 20 minutes. The moisture content of the raw pellets is 7.9%, and the particle size is 10-13 mm.

[0042] The performance of the green pellets is as follows: 4.5 drops per pellet, 9.2 N compressive strength per pellet, and bursting temperature >600℃.

[0043] S3. After drying the green pellets obtained in step S2, preheat them at 950℃ for 20 min, calcine them at 1250℃ for 12 min, and then cool them to obtain sulfuric acid residue oxidized pellets.

[0044] The compressive strength of the sulfuric acid residue oxidized pellets prepared in Comparative Example 1 was 2541 N / pellet.

[0045] Comparative Example 2 S1. Take completely dried magnetite concentrate powder with a TFe grade of 56% and a <0.074mm particle size ratio of 96%, and completely dried sulfuric acid slag with a TFe grade of 59.9% and a <0.074mm particle size ratio of 98%, and bentonite, and mix them to obtain a homogenized mineral powder. The mass ratio of magnetite concentrate is 92%, the mass ratio of sulfuric acid slag is 6%, and the mass ratio of bentonite is 2%.

[0046] S2. The mixed mineral powder from step S1 is pelletized in a disc pelletizer for 20 minutes. The moisture content of the green pellets is 9.4%, and the particle size of the green pellets is 10-13 mm.

[0047] The performance of the green pellets is as follows: 4.1 drops per pellet, 8.7 N compressive strength per pellet, and bursting temperature >600℃.

[0048] S3. After drying the green pellets obtained in step S2, preheat them at 950℃ for 20 min, calcine them at 1250℃ for 12 min, and then cool them to obtain sulfuric acid residue oxidized pellets.

[0049] The compressive strength of the sulfuric acid residue oxidized pellets prepared in Comparative Example 2 was 2483 N / pellet.

[0050] Example 1 S1. Take completely dried magnetite concentrate powder with a TFe grade of 56% and a <0.074mm particle size of 96% and mix it with bentonite to obtain the first mixed mineral powder. The magnetite concentrate has a mass ratio of 98% and the bentonite has a mass ratio of 2%.

[0051] S2. Take completely dried magnetite concentrate powder with a TFe grade of 56% and a <0.074mm particle size ratio of 96%, and completely dried sulfuric acid slag with a TFe grade of 59.9% and a <0.074mm particle size ratio of 98%, and mix it with bentonite to obtain a second blended mineral powder. The magnetite concentrate has a mass ratio of 93%, the sulfuric acid slag has a mass ratio of 5%, and the bentonite has a mass ratio of 2%.

[0052] S3. Take completely dried magnetite concentrate powder with a TFe grade of 56% and a <0.074mm particle size ratio of 96%, and completely dried sulfuric acid slag with a TFe grade of 59.9% and a <0.074mm particle size ratio of 98%, and mix it with bentonite to obtain a third blended mineral powder. The magnetite concentrate has a mass ratio of 90%, the sulfuric acid slag has a mass ratio of 8%, and the bentonite has a mass ratio of 2%.

[0053] S4. The first mixed mineral powder is used to make mother balls in a disc pelletizer. The pelletizing time is 5 minutes, the moisture content of the mother balls is 7.2%, and the particle size of the mother balls is 3~6 mm.

[0054] S5. Add the second and third mixed mineral powders to the mother pellet in sequence to form green pellets. The pelleting time is 10 min and 5 min respectively. The mass ratio of sulfuric acid residue is 6%. The moisture content of the green pellets is 9.1%. The particle size of the green pellets is 10~13 mm.

[0055] The performance of the green pellets is as follows: 4.8 drops per pellet, 9.8 N compressive strength per pellet, and bursting temperature >600℃.

[0056] S6. After drying the obtained green pellets, preheat them at 950℃ for 20 min, calcine them at 1250℃ for 12 min, and then cool them to obtain sulfuric acid residue oxidized pellets.

[0057] The compressive strength test result of the sulfuric acid residue oxidation pellets was 2657 N / piece.

[0058] This application conducts performance testing on iron pellets in accordance with the standards GB / T14201-2018 "Determination of compressive strength of iron pellets for blast furnace and direct reduction" and GB / T27692-2011 "Acidic iron pellets for blast furnace".

[0059] Table 1 shows the mass of sulfuric acid residue oxidation pellets in the comparative and examples.

[0060] Table 1. Mass of sulfuric acid residue oxidation pellets

[0061] This invention proposes a method for strengthening sulfuric acid slag oxidation pellets. By adding sulfuric acid slag, a solid waste resource, to the pellet raw materials, sulfuric acid slag oxidation pellets are prepared, improving the utilization rate of sulfuric acid slag and helping to alleviate the problems of land occupation and environmental pollution caused by sulfuric acid slag accumulation. For low-grade pellet ore, sulfuric acid slag oxidation pellets increase the TFe grade, thereby improving the grade of the feed material to the blast furnace. Using sulfuric acid slag as a solid waste resource reduces the cost of pellet raw materials. By preparing mother pellets with magnetite concentrate and a binder, the adverse effects of poor pelletizing performance caused by sulfuric acid slag are reduced. During the pelletizing process, the addition of sulfuric acid slag mixtures with different gradient proportions allows the green pellets to grow continuously, controlling the gradient distribution of moisture and the density of the green pellets. This solves the problem of large shrinkage after roasting of sulfuric acid slag pellets, improving the mechanical strength of the green pellets and the compressive strength of the oxidation pellets. The sulfuric acid slag oxidation pellets prepared by this method have qualified compressive strength and good metallurgical properties, making them valuable for application and promotion.

[0062] The above are exemplary embodiments disclosed in this invention. The order of the disclosed embodiments is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. However, it should be noted that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of this invention (including the claims) is limited to these examples. Various changes and modifications can be made without departing from the scope defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular.

[0063] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for enhancing the oxidation of sulfuric acid residue into pellets, characterized in that, Includes the following steps: S1. Mixing magnetite concentrate powder with a binder to obtain a first mixed ore, mixing magnetite concentrate powder, sulfuric acid residue with a binder to obtain a second mixed ore, and mixing magnetite concentrate powder, sulfuric acid residue with a binder to obtain a third mixed ore, wherein the mass percentage of sulfuric acid residue in the second mixed ore is lower than the mass percentage of sulfuric acid residue in the third mixed ore. S2. The first mixed ore is made into a first pellet in a disc pelletizer, the second mixed ore is added to the first pellet to make a second pellet, and the third mixed ore is added to the second pellet to make a third pellet; S3. The third pellet is dried, preheated, roasted and cooled to obtain sulfuric acid slag oxidation pellets; By mass percentage, the amount of sulfuric acid slag added to the second mixed ore is 2-6%, and the amount of sulfuric acid slag added to the third mixed ore is 6-10%. The moisture content of the first pellet is controlled at 7-8%, the moisture content of the second pellet is controlled at 7-9%, and the moisture content of the third pellet is controlled at 7-10%.

2. The method for strengthening the oxidation of sulfuric acid slag into pellets according to claim 1, characterized in that, The TFe grade in the magnetite concentrate is 53-56%, and the TFe grade in the sulfuric acid residue is 58-62%.

3. The method for strengthening the oxidation of sulfuric acid slag into pellets according to claim 1, characterized in that, The binder includes bentonite, and the amount of the binder added is 1-3% by mass percentage.

4. The method for strengthening the oxidation of sulfuric acid slag pellets according to claim 1, characterized in that, In step S2, the pelletizing time for the first pellet is 5-6 minutes, the pelletizing time for the second pellet is 8-12 minutes, and the pelletizing time for the third pellet is 5-6 minutes.

5. The method for strengthening the oxidation of sulfuric acid slag into pellets according to claim 1, characterized in that, The particle size of the first pellet is controlled to be 3-6 mm, the particle size of the second pellet is controlled to be 6-10 mm, and the particle size of the third pellet is controlled to be 10-13 mm.

6. The method for strengthening the oxidation of sulfuric acid slag into pellets according to claim 1, characterized in that, The magnetite concentrate is completely dried, and the proportion of particles <0.074mm is 90~98%.

7. The method for strengthening the oxidation of sulfuric acid slag into pellets according to claim 1, characterized in that, The sulfuric acid residue is completely dried, and the proportion of particles <0.074mm is 96~98%.

8. The method for strengthening the oxidation of sulfuric acid slag into pellets according to claim 1, characterized in that, The drying temperature range is 100~115℃, the preheating temperature range is 900℃~1000℃, and the calcination temperature range is 1230℃~1260℃.

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