Method for improving the sphericity of hydrogen-based shaft furnace oxidized pellets
By mechanically activating magnetite concentrate and hematite and using organic composite binders and fluxes, the pellet structure was optimized, solving the problem of easy pulverization of oxidized pellets in hydrogen-based vertical furnace processes, and achieving high-efficiency reduction performance and stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2026-01-31
- Publication Date
- 2026-05-29
AI Technical Summary
Existing technologies are insufficient to effectively improve the structural strength and thermal stability of oxidized pellets in hydrogen-based vertical shaft furnace processes, leading to easy pulverization of pellets during high-temperature reduction, which affects reduction efficiency and production capacity.
By mechanically activating magnetite concentrate and hematite, and combining the use of organic composite binders and fluxes, the physicochemical structure of the pellets is optimized. This process includes steps such as high-pressure roller milling, pelletizing, drying, preheating roasting, and oxidative roasting, resulting in oxidized pellets with highly active lattice defects and an internal liquid phase.
It significantly improves the pelletizing rate of oxidized pellets, enhances the anti-pulverization performance of pellets, ensures the stability and efficiency of the reduction process, and meets the industrialization requirements of hydrogen-based vertical shaft furnace processes.
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Figure CN122105108A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of iron and steel metallurgy technology and relates to a method for improving the pelletization rate of hydrogen-based vertical shaft furnace oxidation pellets. Background Technology
[0002] Against the backdrop of global carbon neutrality, low-carbon metallurgy has become a strategic focus for the transformation and upgrading of my country's steel industry. The steel industry accounts for approximately 15% of the nation's total carbon emissions, with the blast furnace-converter long-process technology, heavily reliant on fossil fuels, emitting as much as 1.6 to 2.2 tons of CO2 per ton of steel. In contrast, the short-process technology centered on the "all-hydrogen vertical shaft furnace-electric furnace" can reduce carbon emissions by over 70%, representing a key path to achieving green and low-carbon development in the steel industry.
[0003] However, the industrial-scale promotion of hydrogen-based vertical shaft furnace technology is limited by the adaptability of raw materials and the stability of the reduction process. Hydrogen reduction is a strongly endothermic reaction, and H2 has a strong reducing power and a small molecular diameter. Under high-temperature reduction conditions, oxide pellets are prone to generating enormous volumetric stress due to the abnormal growth of iron whiskers, inducing abnormal expansion and structural fragmentation. This pulverization phenomenon not only leads to deterioration of the permeability of the furnace charge column and disordered airflow distribution, reducing reduction efficiency, but also causes a series of problems such as furnace nodule formation, reduced capacity, and increased environmental pressure. Therefore, how to synergistically improve the structural strength and thermal stability of pellets during hydrogen-based reduction, and increase the "whole pellet rate," has become a key technical bottleneck restricting the efficient and smooth operation of hydrogen-based vertical shaft furnace technology. Existing technologies typically alleviate pulverization by increasing the charge strength of oxide pellets or using a single chemical additive. However, under the extreme kinetic conditions of all-hydrogen reduction, a single approach often fails to simultaneously address the reduction kinetics and thermal stability of the pellets. Therefore, how to optimize the physicochemical structure of pellets through multi-dimensional means and develop a high-performance pellet preparation technology that can adapt to hydrogen-based vertical furnace reduction has become an urgent problem to be solved in the field of hydrogen metallurgy. Summary of the Invention
[0004] To address the aforementioned problems, this invention provides a method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets.
[0005] This invention provides a method for improving the pelletizing rate of hydrogen-based vertical shaft furnace oxidation pellets, comprising the following steps:
[0006] S1. After blending magnetite concentrate and hematite, mechanical activation is performed. The mechanically activated iron ore raw material, organic composite binder and flux are mixed and then pelletized to obtain qualified green pellets.
[0007] S2. The green pellets obtained in step S1 are dried and preheated and calcined in sequence to obtain preheated pellets;
[0008] S3. The preheated pellets obtained in step S2 are subjected to oxidative calcination to obtain oxidized pellets;
[0009] S4. The oxidized pellets obtained in step S3 are subjected to hydrogen-based reduction behavior detection.
[0010] In a preferred embodiment, in step S1, magnetite concentrate accounts for 20-80 wt% of the iron ore raw material, and hematite accounts for 20-80 wt% of the iron ore raw material. The iron grade of the magnetite concentrate is >67%, and Al2O3+SiO2 <2.5%. The iron grade of the hematite is 61-65%, and Al2O3+SiO2 is 5-10%.
[0011] In the preferred embodiment, in step S1, magnetite concentrate, hematite and water are mixed and then subjected to high-pressure roller milling, with the amount of water added accounting for 4.5~8.0 wt% of the iron ore raw material; the high-pressure roller milling changes the crystal lattice of the iron ore raw material and improves the reaction activity.
[0012] In the preferred embodiment, in step S1, the iron ore raw material after high-pressure roller milling has a thickness of over 95% -0.074mm and a specific surface area of 1600~1800 cm². 2 / g; The high-pressure roller mill is a closed-loop circulation, and the edge material ratio is 50~200%.
[0013] A vibrating screen is installed at the discharge end of the roller mill. The vibrating screen divides the discharge into two parts: the finished material with the required particle size goes directly to the next process or is stored; the coarse particles that exceed the size limit are returned to the feed inlet of the high-pressure roller mill by the conveying equipment for high-pressure roller milling again. This cycle of "roller milling → grading → return material for re-roller milling" constitutes the closed-loop system of the high-pressure roller mill.
[0014] In a preferred embodiment, in step S1, the amount of the organic composite binder added is 0.05~1.5wt% of the total material; more preferably, it is 0.05~1wt%.
[0015] The organic composite binder includes polyacrylamide and black humic acid, with a mass ratio of polyacrylamide to black humic acid of (9~9.5):(0.5~1).
[0016] Using polyacrylamide and black humic acid as composite binders can effectively reduce the amount of bentonite added, thereby improving the iron grade of the finished pellets and facilitating the reduction of slag and energy consumption in subsequent electric arc furnace steelmaking.
[0017] In a preferred embodiment, in step S1, the flux is one or a combination of two of calcium ferrite and steel slag, and the mass ratio of the binary basicity CaO / SiO2 of the mixture is controlled to be 0.15~0.35.
[0018] The composition of the calcium ferrite is as follows: Fe2O3 content is 60%~74%, CaO content is 26%~35%, and Al2O3+SiO2 content is 0%~5%.
[0019] The steel slag has the following composition: Fe2O3 content is 10-30%, CaO content is 30-60%, Al2O3 content is 1-5%, and SiO2 content is 10-20%.
[0020] Calcium ferrite and steel slag are used as fluxes. By adding calcium ferrite and steel slag, the alkalinity of the finished pellets is adjusted to form a liquid phase, which improves the internal stress resistance of the pellets and reduces the pulverization rate.
[0021] By strictly controlling the binary basicity of the mixture to 0.15~0.35, if the basicity is too low, the pelletizing rate will be low; if the basicity is too high, the iron grade of the oxidized pellets will be low, and the amount of slag in subsequent smelting will be large.
[0022] In the preferred embodiment, in step S1, a disc pelletizer is used to pelletize the pellets. The pellet moisture content is 8-12 wt%, the pelletizing time is 8-14 min, and the particle size of the prepared green pellets is 10-16 mm.
[0023] In the preferred embodiment, the green pellets prepared in step S1 achieve the following properties: drop strength greater than 4 times / (0.5mm), compressive strength exceeding 10N / pellet, and bursting temperature exceeding 500℃.
[0024] In a preferred embodiment, in step S2, the drying process involves drying the green pellets under flowing air at a temperature of 220~350℃ for 4~8 minutes.
[0025] In a preferred embodiment, in step S2, the preheating and calcination temperature is 800~950℃ and the time is 6~15min.
[0026] In a preferred embodiment, in step S3, the oxidation calcination temperature is 1160~1220℃ and the time is 12~15min, resulting in an oxidized pellet with a compressive strength >2800N / pellet.
[0027] In a preferred embodiment, step S4 includes detecting the hydrogen-based reduction behavior, including the degree of reduction index, reduction expansion, and low-temperature reduction pulverization; the low-temperature reduction pulverization employs the HYL / Midrex method.
[0028] This invention effectively improves the particle morphology and particle size distribution of magnetite concentrate and hematite through mechanical activation, which is beneficial for subsequent hydrogen-based shaft furnace smelting. Simultaneously, the added flux promotes the generation of a liquid phase within the pellets, increasing the pellet yield. This invention features a simple process that is easy to integrate into existing production lines, providing an efficient and reliable solution for the stable production of high-quality direct reduced iron feedstock from magnetite concentrate and hematite.
[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0030] This invention significantly improves the reduction and pulverization performance of magnetite concentrate and hematite in subsequent oxide pellet production through mechanical activation treatment. The specific surface area of the raw materials after mechanical activation is controlled within an optimized range of 1600-1800 cm² / g, ensuring excellent pelletizing performance while avoiding process problems caused by excessive fineness. This process effectively enhances the interparticle bonding force during pelletizing by significantly increasing the content of high-surface-energy fine particles in the raw materials, thereby significantly improving the drop strength of green pellets. More importantly, the strong mechanical activation effect generated by high-pressure roller milling creates a large number of newly formed, highly active lattice defects and reaction sites on the surface and inside of the mineral particles. These highly active sites greatly promote the conversion efficiency of Fe3O4 to Fe2O3 and the diffusion and consolidation of newly formed hematite microcrystals during subsequent oxidative roasting, ultimately forming a microstructure of oxide pellets with strong intergranular bonding, uniform structure, and density. This mechanically activated and synthesized reinforced structure effectively resists the enormous internal stress generated by lattice transformation and volume change in the reducing environment (Fe2O3→Fe3O4) of a gas-based vertical shaft furnace, thus fundamentally suppressing the tendency of pellets to pulverize during reduction. Simultaneously, the addition of flux (containing calcium-rich materials) and control of the binary basicity of the mixture (CaO / SiO2 mass ratio) to 0.15~0.35 increase the amount of liquid phase inside the oxide pellets, with the liquid phase acting as a binder to aid in the consolidation of the oxide pellets. This process has minimal impact on the iron grade of the oxide pellets entering the hydrogen-based vertical shaft furnace. Without significantly adjusting the preheating and roasting process, qualified oxide pellets are obtained, and the overall pellet yield of high-grade ore is greatly improved.
[0031] Therefore, this invention, through a coupled process of mechanical activation, chemical activation, and ore blending, addresses the challenges of high-grade magnetite concentrate, which is expensive and scarce. By employing a blending scheme of hematite and magnetite concentrate, the pellet yield of high-grade pellets can be significantly improved without altering the existing main processes and formulations. This scheme is simple, easy to modify, and cost-controllable, demonstrating excellent prospects for industrial application. Attached Figure Description
[0032] Figure 1 This is a process flow diagram of the present invention for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets. Detailed Implementation
[0033] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.
[0034] Unless otherwise stated, the magnetite concentrate used in the following comparative examples and embodiments has the following properties:
[0035] Chemical composition: Total iron content 70.16 wt%, SiO2 1.38 wt%, Al2O3 0.88 wt%;
[0036] Physical properties: The raw ore particle size of -0.074 mm is 94.78 wt%, and the specific surface area is 1099 cm². 2 / g.
[0037] The limestone has a CaO content of 49.04 wt%.
[0038] The properties of the hematite used are as follows:
[0039] Chemical composition: Total iron content 66.29 wt%, SiO2 2.76 wt%, Al2O3 0.59 wt%;
[0040] Physical properties: 95% of the raw ore has a particle size of -0.074 mm, and a specific surface area of 1200 cm². 2 / g;
[0041] The present invention will be further described below with reference to specific embodiments and accompanying drawings:
[0042] Comparative Example 1
[0043] S1. Mix 70wt% magnetite concentrate and 30wt% hematite, then add an appropriate amount of water to adjust the moisture content to 8.0wt%.
[0044] S2. Feed the iron ore raw material with a moisture content of 8.0 wt% into a high-pressure roller mill, with a roller mill pressure of 1.17 N / mm. 2 The feeding rate was 6 kg / min, the roller milling was performed once, and there was no edge material recycling. The mechanically activated iron ore raw material had a -0.074 mm content of 97.42 wt% and a specific surface area of 1276 cm². 2 / g.
[0045] S3. Add 1.0 wt% bentonite to the iron ore raw material after high-pressure roller milling, and mix the material thoroughly. The basicity of the mixture is 0.05.
[0046] S4. The dispersed mixture is pelletized on a disc pelletizer for 12 minutes, with atomized water added during the process, to obtain qualified green pellets with a diameter of 10-16 mm and a moisture content of 8.5 wt%. The green pellets have a drop strength of 4.3 times / (0.5 m), a compressive strength higher than 10 N / pellet, and a bursting temperature higher than 600℃.
[0047] S5. The green pellets were dried, preheated, calcined and cooled using a simulated chain grate-rotary kiln process. The drying temperature was 280℃ and the time was 4 min; the preheating temperature was 950℃ and the preheating time was 15 min; the calcination temperature was 1150℃ and the calcination time was 15 min. The compressive strength of the resulting oxidized pellets was 2884 N / pellet.
[0048] S6. The low-temperature reduction pulverization performance of the oxidized pellets was determined, and the low-temperature reduction pulverization LTD was calculated. +6.3 It is 74.72 wt%, LTD -3.2 The content was 13.73 wt%, and the whole ball rate was 55.49%, both of which failed to meet the standards.
[0049] Comparative Example 2
[0050] S1. Mix 70wt% magnetite concentrate and 30wt% hematite, then add an appropriate amount of water to adjust the moisture content to 8.0wt%.
[0051] S2. Feed the iron ore raw material with a moisture content of 8.0 wt% into a high-pressure roller mill, with a roller mill pressure of 1.17 N / mm. 2 The feeding rate was 6 kg / min, the roller milling was performed four times, the edge material ratio was 75%, and the mechanically activated iron ore raw material had a -0.074 mm content of 98.84 wt% and a specific surface area of 1861 cm². 2 / g.
[0052] S3. Add 1.0 wt% bentonite to the magnetite concentrate after high-pressure roller milling, and mix the materials thoroughly. The basicity of the mixture is 0.25.
[0053] S4. The dispersed mixture is pelletized on a disc pelletizer for 12 minutes. Atomized water is added during the process to obtain qualified green pellets with a diameter of 10-16 mm and a moisture content of 9.0 wt%. The drop strength of the green pellets is 5.9 times / (0.5 m), the compressive strength is higher than 10 N / pellet, and the bursting temperature is higher than 600 ℃.
[0054] S5. The green pellets were dried, preheated, calcined and cooled using a simulated chain grate-rotary kiln process. The drying temperature was 300℃ and the time was 4 min; the preheating temperature was 950℃ and the preheating time was 15 min; the calcination temperature was 1200℃ and the calcination time was 15 min. The compressive strength of the resulting oxidized pellets was 2835 N / pellet.
[0055] S6. The low-temperature reduction pulverization performance of the oxidized pellets was determined, and the low-temperature reduction pulverization LTD was calculated. +6.3mm 69.62 wt%, LTD -3.2mm The content was 10.07 wt%, and the whole ball rate was 27.28%, both of which failed to meet the standards.
[0056] Comparative Example 3
[0057] S1. Mix 70wt% magnetite concentrate and 30wt% hematite, then add an appropriate amount of water to adjust the moisture content to 8.0wt%.
[0058] S2. Feed the iron ore raw material with a moisture content of 8.0 wt% into a high-pressure roller mill, with a roller mill pressure of 1.17 N / mm. 2 The feeding rate was 6 kg / min, the roller milling was performed twice, the edge material ratio was 100%, and the mechanically activated magnetite concentrate had a -0.074 mm content of 98.86 wt% and a specific surface area of 1705 cm². 2 / g.
[0059] S3. Add 1.0 wt% bentonite and an appropriate amount of limestone to the magnetite concentrate after high-pressure roller milling, and mix the materials thoroughly. The alkalinity of the mixture is 0.6.
[0060] S4. The dispersed mixture is pelletized on a disc pelletizer for 12 minutes. Atomized water is added during the process to obtain qualified green pellets with a diameter of 10-16 mm and a moisture content of 8.5 wt%. The drop strength of the green pellets is 8.8 times / (0.5 m), the compressive strength is higher than 10 N / pellet, and the bursting temperature is higher than 600 ℃.
[0061] S5. The green pellets were dried, preheated, calcined and cooled using a simulated chain grate-rotary kiln process. The drying temperature was 320℃ and the time was 3 min; the preheating temperature was 950℃ and the preheating time was 15 min; the calcination temperature was 1250℃ and the calcination time was 15 min. The compressive strength of the resulting oxidized pellets was 3026 N / pellet.
[0062] S6. The low-temperature reduction pulverization performance of the oxidized pellets was determined, and the low-temperature reduction pulverization LTD was calculated. +6.3mm 23.94 wt%, LTD -3.2mm The content was 23.47 wt%, and the whole ball rate was 10.24%, both of which failed to meet the standards.
[0063] Example 1
[0064] A method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets, such as Figure 1 As shown, it includes the following steps:
[0065] S1. Mix 70wt% magnetite concentrate and 30wt% hematite, then add an appropriate amount of water to adjust the moisture content to 8.0wt%.
[0066] S2. Feed the iron ore raw material with a moisture content of 8.0 wt% into a high-pressure roller mill, with a roller mill pressure of 1.17 N / mm. 2The feeding rate was 6 kg / min, the roller milling was performed twice, the edge material ratio was 75%, and the mechanically activated magnetite concentrate had a -0.074 mm content of 97.42 wt% and a specific surface area of 1676 cm². 2 / g.
[0067] S3. Add 1.0 wt% organic composite binder (polyacrylamide and black humic acid in a mass ratio of 9:1), appropriate amount of calcium ferrite and steel slag (in a mass ratio of 1:1) to the magnetite concentrate after high pressure roller milling, and mix the materials thoroughly. The basicity of the mixture is 0.35.
[0068] S4. The dispersed mixture is pelletized on a disc pelletizer for 12 minutes, with atomized water added during the process, to obtain qualified green pellets with a diameter of 10-16 mm and a moisture content of 9.0 wt%. The green pellets have a drop strength of 4.5 times / (0.5 m), a compressive strength higher than 10 N / pellet, and a bursting temperature higher than 600 ℃.
[0069] S5. The green pellets were dried, preheated, calcined and cooled using a simulated chain grate-rotary kiln process. The drying temperature was 280℃ and the time was 4 min; the preheating temperature was 950℃ and the preheating time was 15 min; the calcination temperature was 1200℃ and the calcination time was 15 min. The compressive strength of the resulting oxidized pellets was 3164 N / pellet.
[0070] S6. The low-temperature reduction pulverization performance of the oxidized pellets was determined, and the low-temperature reduction pulverization LTD was calculated. +6.3mm 95.91 wt%, LTD -3.2mm It was 2.87 wt%, and the whole ball rate was 83.89%.
[0071] Example 2
[0072] A method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets includes the following steps:
[0073] S1. Mix 70wt% magnetite concentrate and 30wt% hematite, then add an appropriate amount of water to adjust the moisture content to 8.0wt%.
[0074] S2. Feed the iron ore raw material with a moisture content of 8.0 wt% into a high-pressure roller mill, with a roller mill pressure of 1.17 N / mm. 2 The feeding rate was 6 kg / min, the roller milling was performed twice, the edge material ratio was 150%, and the mechanically activated magnetite concentrate had a -0.074 mm content of 98.84 wt% and a specific surface area of 1761 cm². 2 / g.
[0075] S3. Add 1.0 wt% organic composite binder (polyacrylamide and black humic acid in a mass ratio of 9:1), appropriate amount of calcium ferrite and steel slag (in a mass ratio of 1:1) to the magnetite concentrate after high pressure roller milling, and mix the materials thoroughly. The basicity of the mixture is 0.35.
[0076] S4. The dispersed mixture is pelletized on a disc pelletizer for 12 minutes, with atomized water added during the process, to obtain qualified green pellets with a diameter of 10-16 mm and a moisture content of 8.0 wt%. The green pellets have a drop strength of 5.8 times / (0.5 m), a compressive strength higher than 10 N / pellet, and a bursting temperature higher than 600 ℃.
[0077] S5. The green pellets were dried, preheated, calcined and cooled using a simulated chain grate-rotary kiln process. The drying temperature was 320℃ and the time was 4 min; the preheating temperature was 950℃ and the preheating time was 15 min; the calcination temperature was 1200℃ and the calcination time was 15 min. The compressive strength of the resulting oxidized pellets was 2977 N / pellet.
[0078] S6. The low-temperature reduction pulverization performance of the oxidized pellets was determined, and the low-temperature reduction pulverization LTD was calculated. +6.3mm 96.60 wt%, LTD -3.2mm It was 2.64 wt%, with a whole ball rate of 91.28%.
[0079] Comparative Example 1, using a single high-pressure roller mill, suffered from insufficient mechanical activation, resulting in limited improvement in the specific surface area of the magnetite concentrate and inadequate optimization of particle morphology and size distribution. During the reduction process, the lattice parameters changed due to the reduction of Fe2O3 to Fe3O4. This significant change in lattice volume generated substantial internal stress within the pellets, leading to cracks, structural damage, and a high reduction pulverization rate. Comparative Example 2, using four high-pressure roller mills, showed that excessive high-pressure milling resulted in overly fine raw material particles and an excessively dense microstructure in the prepared green pellets. This severely hindered the internal diffusion of oxygen during subsequent oxidative roasting, leading to incomplete oxidation within the pellets and ultimately forming an abnormal structure with significant delamination defects. During the simulated reduction process, this delamination structure caused a severe asynchrony in the reduction progress between the inner and outer layers of the pellets: the outer layer rapidly reduced and shrank while the inner layer reacted more slowly. The resulting enormous internal stress caused cracks in the pellets, eventually leading to surface peeling and severe pulverization. The binary basicity of the mixture in Comparative Example 3 is 0.6. If the basicity is too high, the iron grade of the oxidized pellets will be low, resulting in a large amount of slag in the subsequent smelting.
[0080] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets, characterized in that, include: S1. After blending magnetite concentrate and hematite, mechanical activation is performed. The mechanically activated iron ore raw material, organic composite binder and flux are mixed and then pelletized to obtain qualified green pellets. S2. The green pellets obtained in step S1 are dried and preheated and calcined in sequence to obtain preheated pellets; S3. The preheated pellets obtained in step S2 are subjected to oxidative calcination to obtain oxidized pellets; S4. The oxidized pellets obtained in step S3 are subjected to hydrogen-based reduction behavior detection.
2. The method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets according to claim 1, characterized in that, In step S1, magnetite concentrate accounts for 20-80 wt% of the iron ore raw material, and hematite accounts for 20-80 wt% of the iron ore raw material. The iron grade of the magnetite concentrate is >67%, and Al2O3+SiO2 <2.5%. The iron grade of the hematite is 61-65%, and Al2O3+SiO2 is 5-10%.
3. The method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets according to claim 1, characterized in that, In step S1, magnetite concentrate, hematite and water are mixed and then subjected to high-pressure roller milling. The amount of water added accounts for 4.5 to 8.0 wt% of the iron ore raw material.
4. The method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets according to claim 1, characterized in that, In step S1, after high-pressure roller milling, the iron ore raw material has a thickness of over 95% -0.074mm and a specific surface area of 1600~1800 cm². 2 / g; The high-pressure roller mill is a closed-loop circulation, and the edge material ratio is 50~200%.
5. The method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets according to claim 1, characterized in that, In step S1, the amount of the organic composite binder added is 0.05~1.5 wt% of the total material; The organic composite binder includes polyacrylamide and black humic acid, with a mass ratio of polyacrylamide to black humic acid of (9~9.5):(0.5~1).
6. The method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets according to claim 1, characterized in that, In step S1, the flux is one or a combination of two of calcium ferrite and steel slag, and the mass ratio of the binary basicity CaO / SiO2 of the mixture is controlled to be 0.15~0.
35. The composition of the calcium ferrite is as follows: Fe2O3 content is 60%~74%, CaO content is 26%~35%, and Al2O3+SiO2 content is 0%~5%. The steel slag has the following composition: Fe2O3 content is 10-30%, CaO content is 30-60%, Al2O3 content is 1-5%, and SiO2 content is 10-20%.
7. The method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets according to claim 1, characterized in that, In step S1, a disc pelletizer is used to pelletize the pellets. The pellet moisture content is 8-12 wt%, the pelletizing time is 8-14 min, and the particle size of the prepared green pellets is 10-16 mm. The prepared green pellets achieve the following properties: drop strength greater than 4 times / (0.5mm), compressive strength exceeding 10N / pellet, and bursting temperature exceeding 500℃.
8. The method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets according to claim 1, characterized in that, In step S2, the drying process involves drying the green pellets under flowing air at a temperature of 220-350°C for 4-8 minutes. In step S2, the preheating and calcination temperature is 800~950℃ and the time is 6~15min.
9. The method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets according to claim 1, characterized in that, In step S3, the oxidation calcination temperature is 1160~1220℃, the time is 12~15min, and the compressive strength of the resulting oxidized pellets is >2800N / pellet.
10. The method for improving the pellet yield of hydrogen-based vertical shaft furnace oxidation pellets according to claim 1, characterized in that, In step S4, the detection of hydrogen-based reduction behavior includes reduction index, reduction expansion, and low-temperature reduction pulverization; The low-temperature reduction pulverization was performed using the HYL / Midrex method.