Vanadium-titanium sinter reduction molten drop improving method based on hydrogen-rich gas injection

Abstract

The invention discloses a method for improving the reduction molten drop property of vanadium-titanium sinter based on hydrogen-rich gas injection, and relates to the technical field of iron and steel smelting. Determining core characteristic parameters of the vanadium-titanium sinter and parameters of a blast furnace injection system, constructing a multi-element injection mode, and regulating and controlling the proportion of reducing gas of hearth gas; then carrying out an isothermal reduction experiment, obtaining reaction process data, product phase information and microstructure characteristics, constructing a kinetic analysis model, and establishing a correlation mechanism between the hydrogen-rich gas input quantity and the reduction reaction process; a hydrogen-rich content gradient experiment scheme is designed, a molten drop performance test is carried out, and the corresponding relation between the hydrogen-rich content and molten drop characteristics is constructed; and optimizing related parameters to form a process regulation and control scheme. According to the method, the reduction atmosphere and the reaction path are optimized through hydrogen-rich gas injection, the reduction efficiency and the molten drop performance of the vanadium-titanium sinter are synergistically improved, generation of harmful phases is inhibited, and technical support is provided for efficient and green smelting of the vanadium-titanium magnetite.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, specifically to a hydrogen-rich gas injection method for directionally improving the reducibility of vanadium-titanium sinter droplets by determining core parameters, constructing a multi-element injection mode, conducting isothermal reduction experiments and droplet performance tests, establishing a kinetic model and optimizing parameters. Background Technology

[0002] As a pillar industry of the national economy, the steel industry plays an irreplaceable role in the global industrialization process. However, traditional blast furnace ironmaking technology has long faced the industry's pain points of high energy consumption and high carbon emissions. Vanadium-titanium magnetite, as an important strategic mineral resource in my country, faces challenges in its smelting process due to the presence of titanium, leading to difficulties in reduction and poor charge melting performance, further exacerbating energy consumption and environmental pressures. Hydrogen-rich smelting technology, with its core advantages of high hydrogen reduction efficiency and low carbon emissions, has become a key path to overcome the bottlenecks of traditional ironmaking processes. How to optimize the reduction and melting performance of vanadium-titanium sinter through hydrogen-rich gas injection to achieve efficient and green smelting of vanadium-titanium magnetite has become a core issue that the industry urgently needs to address.

[0003] The reduction behavior and dripping characteristics of vanadium-titanium sinter directly determine the smoothness of blast furnace smelting, energy utilization, and product quality. In traditional pulverized coal injection (PCI) smelting, CO is the primary reducing medium in the hearth gas. The reduction rate of iron oxides in vanadium-titanium sinter is slow, and harmful phases such as Fe3C are easily generated during reduction, leading to an excessively wide softening range in the burden, deteriorated dripping performance, and consequently, reduced burden permeability and uneven gas flow distribution. Simultaneously, titanium readily forms high-melting-point substances such as TiC at high temperatures, exacerbating slag viscosity and flooding, severely restricting the smelting efficiency of vanadium-titanium magnetite. Therefore, optimizing the composition of the reducing medium, regulating the reduction reaction mechanism, and improving the dripping properties of the burden are key breakthroughs for enhancing the smelting technology of vanadium-titanium magnetite.

[0004] Hydrogen-rich gas injection offers a novel approach to the synergistic optimization of reduction and droplet properties in vanadium-titanium sinter. Hydrogen, as a superior reducing medium, not only offers significant thermodynamic advantages in the reduction reaction but also produces water vapor, effectively reducing the partial pressure of CO in the coal gas and inhibiting the formation of harmful phases. However, the alteration of the CO:H2:N2 ratio in the hearth gas after hydrogen-rich gas injection directly affects the reduction kinetics, phase transformation pathways, and physicochemical behavior of vanadium-titanium sinter during droplet formation. Currently, quantitative research on the effects of hydrogen content on the reduction reaction mechanism and phase evolution of vanadium-titanium sinter is insufficient. The correlation mechanism between key droplet temperature parameters and column permeability under hydrogen-rich atmosphere remains unclear, and a systematic process optimization scheme is lacking, severely limiting the industrial application of hydrogen-rich smelting technology in vanadium-titanium magnetite smelting. Summary of the Invention

[0005] Based on the aforementioned technical problems, this application discloses a method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection, specifically including:

[0006] Determine the core characteristic parameters of vanadium-titanium sinter and the parameters of the blast furnace injection system. The core characteristic parameters include chemical composition, phase composition and pore structure, while the injection system parameters cover hydrogen-rich gas type, injection gradient, hearth gas composition control target and reduction temperature system.

[0007] A multi-mode injection system is constructed, which forms a differentiated injection system by combining hydrogen-rich gas and pulverized coal. The amount of hydrogen-rich gas input is adjusted based on the injection gradient to control the proportion of reducing gas components in the hearth gas.

[0008] Isothermal reduction experiments of vanadium-titanium sinter were carried out under the reduction temperature system. Combined with thermogravimetric analysis, phase detection and micro-characterization techniques, data on the reduction reaction process, product phase information and microstructure characteristics were obtained.

[0009] A kinetic analysis model was constructed based on the reduction reaction process data. The reaction mechanism and kinetic parameters were determined by fitting characteristic functions, and a correlation mechanism between the amount of hydrogen-rich gas input and the reduction reaction process was established.

[0010] Design a gradient hydrogen content experimental scheme, conduct vanadium-titanium sinter droplet performance tests, obtain key temperature correlation data of droplets and air permeability data of material columns, and construct the correspondence between hydrogen content and droplet characteristics.

[0011] Based on the correlation mechanism and corresponding relationship, the injection mode, hydrogen-rich gas input and reduction temperature parameters are optimized to form a process control scheme for the targeted improvement of the reduction droplet properties of vanadium-titanium sinter.

[0012] Preferred multi-element injection modes include single pulverized coal injection mode, hydrogen-pulverized coal combined injection mode, and shale gas-pulverized coal combined injection mode;

[0013] The single pulverized coal injection mode maintains the volume ratio of CO, H2, and N2 in the hearth gas within a preset baseline range by fixing the pulverized coal injection parameters;

[0014] The hydrogen-pulverized coal composite injection mode adjusts the input amount according to the increasing hydrogen-rich gas injection gradient, and simultaneously realizes the dynamic adaptation of CO volume ratio, H2 volume ratio, and N2 volume ratio.

[0015] The shale gas-pulverized coal composite injection mode is based on the inherent component characteristics of shale gas. It adjusts the input amount according to the injection gradient to achieve step-by-step control of the volume ratio of the three gases in the hearth gas.

[0016] Preferably, the two differentiated temperature ranges of the reduction temperature system are divided by a temperature critical value, where the temperature critical value is... Determined through calculations using thermodynamic equilibrium equations: ,in This refers to the enthalpy change of the secondary reaction between the reducing gas and the reduction product. This represents the entropy change of the reaction. This is the critical temperature value;

[0017] When the reduction temperature At this time, the first temperature range that triggers the secondary reaction is formed;

[0018] When the reduction temperature At that time, a second temperature range is formed that blocks the secondary reaction.

[0019] Preferably, the kinetic analysis model construction includes reaction progress quantification, mode function matching, and kinetic parameter calculation, specifically:

[0020] reaction progress pass Quantification, among which For a specific time Actual weight loss under the conditions This represents the theoretical maximum weight loss.

[0021] Construct using feature function fitting method and The linear relationship is shown in the fitted equation as follows: ,in Let A be the characteristic constant of the reaction, E be the pre-exponential factor, R be the activation energy of the reaction, and T be the gas constant. Reaction time;

[0022] Based on the numerical distribution range of the reaction characteristic constant n, the reduction reaction mechanism type is determined and the corresponding reaction mode function is matched. ;

[0023] Reaction rate constant Following the Arrhenius equation The reduction reaction rate is determined by the fundamental kinetic equation. calculate.

[0024] Preferably, the stages of the reduction reaction are divided using a reaction progress threshold. Define and satisfy: ,in The theoretical weight loss for the complete reduction of high-valence iron oxides to low-valence iron oxides;

[0025] when At that time, the reaction system is in the first stage of the transformation from high-valence iron oxide to low-valence iron oxide;

[0026] when At that time, the reaction system is in the second stage of the transformation of low-valent iron oxides into elemental iron.

[0027] Preferably, in the droplet performance test, the furnace charge shrinkage rate is used as the metric. Pressure difference with the material column Dynamic monitoring data, combined with the following correlation formula, are used to obtain the critical temperature correlation data of the molten droplet:

[0028] in The initial shrinkage rate, The temperature coefficient of shrinkage. Reference temperature;

[0029] ,in The initial pressure difference, This is the temperature coefficient of pressure difference;

[0030] By solving and The corresponding temperature values ​​yielded the softening initiation temperature, softening termination temperature, and melting initiation temperature. Combined with the monitoring temperature of the first drop of slag and iron, key temperature correlation data were formed. , To preset the shrinkage rate threshold, This is the preset differential pressure threshold.

[0031] Preferably, the dripping rate and air permeability characteristic value are calculated simultaneously in the droplet performance test, and the calculation method is as follows:

[0032] drip rate pass Calculation, where The total mass of the dripping slag and iron. This refers to the total mass of vanadium-titanium sinter used in the experiment;

[0033] Breathability characteristic value SD passed Calculation, where To soften the initial temperature, The dripping temperature, The pressure difference of the material column at temperature T.

[0034] Preferably, the correlation analysis between the phase and microstructure of the reduction product satisfies:

[0035] Degree of phase transformation ,in , , , The diffraction intensities of elemental Fe and iron oxides in various valence states are respectively.

[0036] Microstructure evolution characteristics are characterized by grain refinement coefficient Quantification, among which The average grain size when no hydrogen-rich gas was injected. The average grain size after hydrogen-rich gas injection;

[0037] Establish , With hydrogen-rich gas input Relationship: , where a, b, c, and d are the fitting coefficients.

[0038] Preferably, the effect of hydrogen-rich gas on the permeability of the feed column satisfies the following relationship:

[0039] Gas flow resistance of the material column ,in This represents the drag coefficient when no hydrogen-rich gas is injected. This is the resistance adjustment coefficient;

[0040] Maximum pressure difference of the material column ,in For the density of coal gas, The gas flow rate is the gas flow rate. The height of the material column, The equivalent diameter of the material column;

[0041] By adjusting the amount of hydrogen-rich gas input ,accomplish Targeted regulation.

[0042] Preferably, the optimized process control scheme satisfies:

[0043] kinetic optimization objective: ,in The activation energy varies with the amount of hydrogen-rich gas input Q. The reaction rate constant varies with temperature T and Q. , For each optimization coefficient;

[0044] Optimization goals for molten droplet performance: ,in , They are respectively The changing drip rate and air permeability characteristic values, , , For each performance optimization coefficient;

[0045] The optimal hydrogen-rich gas input was determined using a multi-objective optimization algorithm. pulverized coal ratio and reduction temperature .

[0046] Compared with the prior art, the technical solution of this application has the following technical effects:

[0047] This invention effectively optimizes the reduction medium environment of vanadium-titanium sinter by constructing a multi-element injection mode and precisely controlling the proportion of gas components in the hearth. The introduction of hydrogen-rich gas not only provides excellent thermodynamic conditions for the reduction of iron oxides, but also changes the path and rate of the reduction reaction by controlling the ratio of CO to H2, thereby achieving directional control of the reduction process and significantly improving the reduction efficiency and metallization degree of vanadium-titanium sinter.

[0048] This invention clarifies the reduction reaction mechanism of vanadium-titanium sinter under a hydrogen-rich atmosphere by scientifically dividing the reduction temperature system and constructing a kinetic analysis model. By suppressing the formation of harmful phases and matching the optimal reaction mode function, the invention ensures the efficient and orderly conduct of the reduction reaction, while reducing the activation energy and enhancing the mass and heat transfer process, thus providing core technical support for improving reduction efficiency.

[0049] This invention achieves targeted optimization of the droplet characteristics of vanadium-titanium sinter by systematically studying the correlation between hydrogen content and droplet performance. The injection of hydrogen-rich gas effectively controls key temperature parameters such as softening, melting and dripping, optimizes the pore distribution of the material layer and the physical properties of the slag, significantly improves the permeability of the material column, reduces the occurrence of flooding, and provides a guarantee for the smooth operation of blast furnace smelting.

[0050] This invention achieves a synergistic improvement in reduction efficiency and droplet performance through a process control scheme determined by a multi-objective optimization algorithm. It can dynamically match key parameters such as hydrogen-rich gas input, pulverized coal injection ratio, and reduction temperature according to actual smelting conditions, taking into account both the needs of green and low-carbon smelting and high-efficiency smelting. This lays a solid foundation for the industrial application of hydrogen-rich smelting technology for vanadium-titanium magnetite.

[0051] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the preferred embodiments of this application are described in detail below with reference to the accompanying drawings.

[0052] The above and other objects, advantages and features of this application will become more apparent to those skilled in the art from the following detailed description of specific embodiments in conjunction with the accompanying drawings. Attached Figure Description

[0053] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0054] Based on the description of the figures and their corresponding technical content in the document, the titles of the figures are as follows:

[0055] Figure 1 Process architecture flow chart of the method for improving the reduction and droplet properties of vanadium-titanium sinter based on hydrogen-rich gas injection;

[0056] Figure 2 XRD patterns of vanadium-titanium sinter after reduction at different temperatures (700℃, 850℃, 1000℃) under pulverized coal injection mode only;

[0057] Figure 3 SEM characterization of the microstructure of vanadium-titanium sinter after reduction at 1000℃ for 10 min under pulverized coal injection mode only;

[0058] Figure 4 Curve of weight loss rate of vanadium-titanium sinter as a function of time and gas composition under hydrogen-pulverized coal combined injection mode.

[0059] Figure 5 Curves showing the change in iron reducibility of vanadium-titanium sinter over time at different temperatures (700℃, 850℃, 1000℃) under hydrogen-pulverized coal combined injection mode.

[0060] Figure 6 Curves showing the change in iron reduction rate of vanadium-titanium sinter at 850℃ and 1000℃ under hydrogen-pulverized coal combined injection mode as a function of reduction progress.

[0061] Figure 7 Scatter plot and fitting graph of ln[-ln(1-α)] versus lnt under different reducing gas compositions in hydrogen-pulverized coal combined injection mode;

[0062] Figure 8 Curve of weight loss rate of vanadium-titanium sinter as a function of time and gas composition under shale gas-pulverized coal combined injection mode;

[0063] Figure 9 Curves showing the change in iron reducibility of vanadium-titanium sinter over time at different temperatures (700℃, 850℃, 1000℃) under the shale gas-pulverized coal combined injection mode.

[0064] Figure 10Curves showing the change in iron reduction rate of vanadium-titanium sinter at 850℃ and 1000℃ under shale gas-pulverized coal combined injection mode as a function of reduction progress.

[0065] Figure 11 Scatter plot and fitting graph of ln[-ln(1-α)] versus lnt under different reducing gas compositions in shale gas-pulverized coal combined injection mode;

[0066] Figure 12 Shrinkage rate-temperature and pressure difference-temperature droplet properties of vanadium-titanium sinter under five different H2 content reducing atmospheres;

[0067] Figure 13 Pressure difference-temperature characteristic curves of vanadium-titanium sinter droplet process under different H2 reducing gas ratios;

[0068] Figure 14 XRD phase analysis spectra of vanadium-titanium sinter molten drop slag after different H2 reducing gas ratios;

[0069] Figure 15 SiO2-CaO-MgO-(Al2O3-TiO2) pentagonal slag phase equilibrium phase diagram (including temperature and mass fraction coordinates). Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. In the following description, specific details such as specific configurations and components are provided merely to help fully understand the embodiments of this application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of this application. In addition, for clarity and brevity, descriptions of known functions and structures are omitted in the embodiments.

[0071] It should be understood that the phrase "an embodiment" or "this embodiment" throughout the specification means that a specific feature, structure, or characteristic related to the embodiment is included in at least one embodiment of this application. Therefore, "an embodiment" or "this embodiment" appearing throughout the specification does not necessarily refer to the same embodiment. Furthermore, these specific features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0072] Furthermore, reference numerals and / or letters may be repeated in different examples within this application. Such repetition is for the purpose of simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0073] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" in this article describes another type of relationship between related objects, indicating that two relationships can exist. For example, A / and B can mean: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the related objects before and after it are in an "or" relationship.

[0074] In this article, the term "at least one" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, "at least one of A and B" can mean: A exists alone, A and B exist simultaneously, or B exists alone.

[0075] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion.

[0076] Example 1

[0077] This embodiment mainly describes a method for improving the reducing droplet properties of vanadium-titanium sinter based on hydrogen-rich gas injection, such as... Figure 1 As shown, it specifically includes:

[0078] Determine the core characteristic parameters of vanadium-titanium sinter and the parameters of the blast furnace injection system. The core characteristic parameters include chemical composition, phase composition and pore structure, while the injection system parameters cover hydrogen-rich gas type, injection gradient, hearth gas composition control target and reduction temperature system.

[0079] A multi-mode injection system is constructed, which forms a differentiated injection system by combining hydrogen-rich gas and pulverized coal. The amount of hydrogen-rich gas input is adjusted based on the injection gradient to control the proportion of reducing gas components in the hearth gas.

[0080] Isothermal reduction experiments of vanadium-titanium sinter were carried out under the reduction temperature system. Combined with thermogravimetric analysis, phase detection and micro-characterization techniques, data on the reduction reaction process, product phase information and microstructure characteristics were obtained.

[0081] A kinetic analysis model was constructed based on the reduction reaction process data. The reaction mechanism and kinetic parameters were determined by fitting characteristic functions, and a correlation mechanism between the amount of hydrogen-rich gas input and the reduction reaction process was established.

[0082] Design a gradient hydrogen content experimental scheme, conduct vanadium-titanium sinter droplet performance tests, obtain key temperature correlation data of droplets and air permeability data of material columns, and construct the correspondence between hydrogen content and droplet characteristics.

[0083] Based on the correlation mechanism and corresponding relationship, the injection mode, hydrogen-rich gas input and reduction temperature parameters are optimized to form a process control scheme for the targeted improvement of the reduction droplet properties of vanadium-titanium sinter.

[0084] The chemical composition of the core characteristic parameters of vanadium-titanium sinter requires precise determination of the mass fractions of CaO, MgO, SiO2, Al2O3, and TiO2, as well as the content ratios of iron oxides in various valence states, such as Fe2O3, Fe3O4, and FeO. These components directly determine the thermodynamic trend of the reduction reaction and the physicochemical properties of the slag. Phase composition needs to be determined by XRD analysis to clarify the existence forms and relative contents of stable phases such as CaTiO3, spinel, and forsterite (Mg2SiO4) in the initial phase, while also predicting the intermediate and final product phases generated during the reduction process, such as Fe3C and elemental Fe. Pore structure needs to be tested using mercury intrusion porosimetry or nitrogen adsorption to obtain porosity, average pore size, pore size distribution curves, and pore connectivity parameters. Differences in pore structure directly affect the mass transfer efficiency of reducing gas within the ore particles. The hydrogen-rich gas types in the blast furnace injection system parameters are limited to high-purity hydrogen (H2 volume fraction ≥ 99.9%) and shale gas (CH4 volume fraction ≥ 90%). The injection gradient is a graded standard that increases at fixed intervals. The hydrogen injection gradient is set to three gradients: 15 kg / tHM, 30 kg / tHM, and 45 kg / tHM. The shale gas injection gradient is set to three gradients: 40 kg / tHM, 80 kg / tHM, and 120 kg / tHM. The target for controlling the composition of the hearth gas is to achieve continuous and adjustable volume ratios of CO, H2, and N2 by adjusting the amount of hydrogen-rich gas input. The reduction temperature system is a differentiated temperature range divided according to the characteristics of the reduction reaction and the phase transformation law. Its critical temperature value is determined by calculation through thermodynamic equilibrium equations, providing a theoretical basis for the selection of subsequent experimental temperature points.

[0085] The construction of the multi-element injection mode uses pulverized coal with a fixed injection ratio of 108 kg / tHM as the basic injection medium. By combining it with two hydrogen-rich gases, three distinct injection systems with clearly defined functions are formed. In the single pulverized coal injection mode, only pulverized coal is injected into the blast furnace tuyeres without introducing additional hydrogen-rich gases. By stabilizing parameters such as the pulverized coal injection rate and blast pressure, the volume ratio of CO, H2, and N2 in the hearth gas is maintained at a preset baseline range of 47:4:49. This ratio is calculated using an energy-mass balance and replacement ratio model, which can simulate the reducing atmosphere of traditional blast furnace smelting. The hydrogen-pulverized coal composite injection mode adjusts the hydrogen input in increments of 15 kg / tHM. The hydrogen injection rates corresponding to the three gradients are 15 kg / tHM, 30 kg / tHM, and 45 kg / tHM, respectively. As the hydrogen input increases, the volume percentage of CO in the hearth gas gradually decreases from 41% to 36% and then to 32%, the volume percentage of H2 gradually increases from 14% to 22% and then to 29%, and the volume percentage of N2 is dynamically adjusted from 45% to 42% and then adapted to 39%. The proportion of gas components under each gradient is precisely controlled through model calculation to ensure the differentiation of the reducing atmosphere. The shale gas-pulverized coal composite injection mode adjusts the shale gas input in stages at intervals of 40 kg / tHM. The shale gas injection rates corresponding to the three gradients are 40 kg / tHM, 80 kg / tHM, and 120 kg / tHM, respectively. Correspondingly, the volume percentage of CO in the hearth gas gradually decreases from 43% to 40% and then to 37%, the volume percentage of H2 gradually increases from 10% to 15% and then to 20%, and the volume percentage of N2 is adjusted stepwise from 47% to 45% and then to 43%. The gradient optimization of the reducing atmosphere is achieved by utilizing the compositional characteristics of shale gas itself.

[0086] The two differentiated temperature ranges of the reduction temperature system are separated by a temperature critical value. Division, The calculations are based on the thermodynamic equilibrium equations of the secondary reactions of reducing gases and reduction products (mainly the reaction of CO with elemental Fe to form Fe3C): ,in This is the standard enthalpy change of the secondary reaction. The standard entropy change is obtained by consulting thermodynamic handbooks or experimental measurements to find an accurate value, which is then substituted into the equation to solve for the result. When the reduction temperature At this temperature, the first temperature range that triggers the secondary reaction is formed. Within this range, the thermodynamic conditions favor the reaction between CO and the reduced elemental Fe, forming the Fe3C phase. The formation of this phase causes abnormal fluctuations in the weight loss curve of the ore sample during reduction and also affects the reduction process of iron oxides. When the reduction temperature... At this point, a second temperature range is formed that blocks the secondary reaction. Within this range, the thermodynamic conditions are unfavorable for the formation of Fe3C, thus preventing the secondary reaction from interfering with the reduction process and ensuring that iron oxides are gradually reduced to elemental Fe along the predetermined path of Fe2O3→Fe3O4→FeO→Fe. This is verified by experiments. The corresponding actual temperature value is approximately 700℃, therefore the first temperature range is set to ≤700℃, and the second temperature range is set to >700℃. Figure 2 The XRD patterns of the reduction products at different temperatures under pulverized coal injection mode shown can intuitively verify the effect of the temperature range division: at 700℃ (first temperature range), the characteristic diffraction peak of Fe3C appears in the spectrum (corresponding to the mark "5" in the figure), indicating that the secondary reaction is triggered in this range; while at 850℃ and 1000℃ (second temperature range), the diffraction peak of Fe3C completely disappears, and only the characteristic peaks of Fe (corresponding to "1" in the figure) and CaTiO3 (corresponding to "2" in the figure) are retained, proving that this range can effectively block the secondary reaction and ensure that the iron oxide is reduced according to the preset path. The two key temperature points of 850℃ and 1000℃ are selected as the core experimental temperatures for kinetic analysis and phase detection experiments. These two temperature points can effectively block the formation of Fe3C and cover the main reduction temperature range of vanadium-titanium sinter in the blast furnace.

[0087] The isothermal reduction experiment was conducted using a high-precision thermogravimetric analyzer. Before the experiment, the vanadium-titanium sinter was crushed and sieved to a particle size of 100-200 mesh. A 10-15 mg sample was then evenly spread in an alumina crucible to ensure uniform heating. During the experiment, the furnace was first heated to the set reduction temperature (700℃, 850℃, or 1000℃). After the temperature stabilized, simulated furnace gas under the corresponding injection mode was introduced, with a gas flow rate controlled at 100 mL / min to ensure a stable reducing atmosphere. During the experiment, the thermogravimetric analyzer recorded the mass change data of the ore sample in real time, with a sampling frequency of once per minute, accurately obtaining the actual weight loss at different reaction times. Simultaneously, after the reduction reaction had proceeded for 10 minutes, the experiment was stopped and the sample was rapidly cooled. XRD analysis was used to qualitatively analyze the phase composition of the reduction products. By comparing standard diffraction patterns, the presence and relative content of phases such as CaTiO3, Fe, Fe3C, spinel, FeO, and MgSiO3 were clarified. SEM characterization was used to observe the microstructure of the reduction products, clearly revealing the geometry and size of unreacted nuclei, the clarity of the reaction interfaces, and the morphological characteristics of the grains. Figure 3As shown, (microstructure after reduction at 1000℃ under pulverized coal injection mode only) are the SEM characterization results under these experimental conditions. It can be observed that the reduction product contains obvious unreacted core structures, surrounded by an "iron shell" of elemental Fe. The unreacted cores are relatively large, and the reaction interface is relatively blurred. Simultaneously, the grains exhibit a relatively coarse morphology. These microscopic features are crucial for subsequent calculations of the grain refinement coefficient. This study provides baseline data and offers a direct basis for analyzing the mass transfer process of reducing gas within mineral particles. During the experiment, parameters such as gas purity (≥99.99%), heating rate (10℃ / min), and reaction time were strictly controlled to ensure the high accuracy and repeatability of the obtained reduction reaction process data, product phase information, and microstructural characteristics, providing reliable data support for subsequent kinetic analysis and correlation model construction.

[0088] Furthermore, the kinetic analysis model is constructed to quantify the reaction progress through the reaction advance: ,in The theoretical maximum weight loss when all reducible oxides (mainly iron oxides) in vanadium-titanium sinter are completely reduced to their elemental state is calculated using the chemical composition of the ore sample. Specifically, based on the content of iron oxides in each valence state and the reduction reaction equation, the theoretical oxygen loss per mole of iron oxide during the reduction process is calculated and then converted into the corresponding mass loss. Subsequently, the ln-ln analysis method is used to construct... and The linear relationship is fitted by the following equation: ,in This is the characteristic constant of the reaction (Avrami constant). Pre-exponential factor, Let be the activation energy, R be the gas constant (8.314 J / (mol·K)), T be the experimentally set absolute temperature, and t be the reaction time. In practice, the values ​​corresponding to different reaction times are extracted from the thermogravimetric data. Value, calculated and The values ​​were used to perform linear fitting using the least squares method to obtain the slope (i.e., the n-value) and intercept of the fitted line. Based on the distribution range of the fitted n-values, the reduction reaction mechanism type was determined and the corresponding reaction mode function was matched by referring to the correspondence table between common gas-solid reaction mode functions and n-values. Experimental results show that at 850℃ and 1000℃, the value of n fluctuates around 1.2, corresponding to a random nucleation followed by growth mechanism. The matching mode function is: Reaction rate constant Following the Arrhenius equation: A and E are calculated using the intercepts obtained from ln-ln fitting, i.e., the intercepts. Given R and T, the specific values ​​of A and E can be obtained. The reduction reaction rate is calculated using the basic kinetic equations: , will be determined and By substituting into the equation, the reduction reaction rate at different reaction stages can be obtained, the correlation mechanism between the amount of hydrogen-rich gas input and the reaction activation energy, reaction rate constant and reaction rate can be established, and the regulation law of hydrogen-rich gas on the kinetic characteristics of reduction reaction can be clarified.

[0089] The stages of a reduction reaction are determined by the reaction progress threshold. Definition: ,in The theoretical weight loss for the complete reduction of high-valence iron oxides (Fe2O3, Fe3O4) to low-valence iron oxides (FeO) in vanadium-titanium sinter is calculated through chemical composition analysis combined with reduction reaction equations. Specifically, based on the reaction equations for the reduction of Fe2O3 to FeO and Fe3O4 to FeO, the oxygen loss when each high-valence iron oxide is completely converted to FeO is calculated, and the results are summed to obtain the final value. .when At this stage, the reaction system is in the first stage, where the core reaction is the transformation of high-valence iron oxides into low-valence iron oxides. This mainly involves the reactions Fe₂O₃ + CO = 2FeO + CO₂, Fe₃O₄ + CO = 3FeO + CO₂, and the corresponding hydrogen reduction reactions. Because the reduction thermodynamic tendency of high-valence iron oxides is stronger and the activation energy of the reaction is relatively low, the reduction reaction rate in this stage is faster. The weight loss curve of the mineral sample shows a significant downward trend. Simultaneously, XRD analysis reveals that the diffraction peak intensities of Fe₂O₃ and Fe₃O₄ gradually decrease, while the diffraction peak intensity of FeO gradually increases. When... At this stage, the reaction system is in the second stage. The core reaction in this stage is the transformation of low-valent iron oxide (FeO) into elemental iron (Fe). The main reactions are FeO + CO = Fe + CO2 and FeO + H2 = Fe + H2O. The activation energy of this reaction is relatively high, and as the reaction proceeds, an iron shell of elemental iron will form on the surface of the ore sample, which to some extent hinders the diffusion of reducing gas into the interior. Therefore, the reduction reaction rate in this stage is relatively slow, the downward trend of the weight loss curve of the ore sample slows down, and XRD detection shows that the diffraction peak intensity of FeO gradually weakens, while the diffraction peak intensity of elemental Fe gradually increases until the diffraction peak of FeO completely disappears, indicating that the reduction reaction is basically completed.

[0090] Furthermore, a vertical droplet furnace was used for the droplet performance test. Before the experiment, the vanadium-titanium sinter was crushed to a particle size of 3-5 mm. 500 g of the ore sample was evenly packed into a graphite crucible. A perforated plate (5 mm aperture) was installed at the bottom of the crucible to collect the dripping slag and iron. During the experiment, the temperature was increased from room temperature to 1600℃ at a rate of 10℃ / min. A reducing gas with a corresponding hydrogen-rich content was introduced throughout the process, with a gas flow rate controlled at 5 L / min. Simultaneously, the shrinkage of the furnace charge was monitored in real time using a displacement sensor, and the pressure difference of the charge column was monitored in real time using a pressure sensor. The sampling frequency for both was once per minute. The furnace charge shrinkage rate was measured. The pressure difference of the charge column is calculated by the ratio of the shrinkage monitored by the displacement sensor to the initial height of the charge. Data is read directly from the pressure sensor and processed using the following correlation: ,in The initial shrinkage rate at room temperature (approximately 0) is given. The shrinkage temperature coefficient is obtained by linearly fitting the relationship between shrinkage rate and temperature. The reference temperature is (room temperature, 25°C). in The initial pressure difference at room temperature (approximately 0). The pressure difference temperature coefficient is obtained by linearly fitting the relationship between the logarithm of the pressure difference and temperature. This is achieved by solving... and The corresponding temperature values ​​yield the softening initiation temperature ( ). ), softening end temperature ( ) and melting initiation temperature ( ),in To preset the shrinkage rate threshold, The preset differential pressure threshold (0.5 kPa) is combined with the temperature of the first drop of slag and iron at the moment of its fall, as monitored by a high-temperature camera. ), forming a collection and softening range ( - ), droplet range ( - ), softening zone ( - The critical temperature correlation data of the melting droplets was used. The droplet rate and air permeability characteristic values ​​were calculated simultaneously. The formula for calculation is: ,in This represents the total mass of dripping slag and iron collected after the experiment. The total mass of vanadium-titanium sinter used in the experiment; the formula for calculating the permeability characteristic value SD is: By analyzing the pressure difference-temperature curve at to The results were obtained by integral calculation within the interval, using the trapezoidal integral method and data processing software, to establish the correspondence between the hydrogen-rich content and the aforementioned droplet characteristic parameters.

[0091] Correlation analysis of the phase and microstructure of reduction products through the degree of phase transformation and grain refinement coefficient Quantification, among which The formula for calculation is: , , , , The values ​​represent the characteristic diffraction peak intensities (based on the highest peak intensity) of elemental Fe and iron oxides in various valence states in the XRD patterns, obtained using XRD detection software. The value ranges from 0 to 1. A value closer to 1 indicates a more complete reduction of the iron oxide. The microstructure evolution characteristics are determined by the grain refinement coefficient. Quantification: ,in The average grain size of elemental Fe in the reduction product when no hydrogen-rich gas is injected (single pulverized coal injection mode) is given. The average grain size of elemental Fe in the reduction product after hydrogen-rich gas injection is given. The grain size was obtained by combining SEM characterization images with ImageJ software measurement. More than 50 grains were randomly selected and their equivalent diameters were measured. The average value was taken as the average grain size under this condition. >1 indicates that hydrogen-rich blowing achieved grain refinement. Establishment , With hydrogen-rich gas input Relationship: Where a, b, c, and d are coefficients obtained by fitting experimental data, specifically by fitting the corresponding values ​​under different amounts of hydrogen-rich gas input. , Substituting the values ​​into the above function, the least squares method is used to determine whether linear or nonlinear fitting is performed. During the fitting process, the correlation coefficient must be ensured. To ensure the reliability of the correlation, this correlation analysis can clarify the quantitative influence of the amount of hydrogen-rich gas input on the degree of phase transformation and the evolution characteristics of microstructure.

[0092] The permeability of the feed column is controlled by hydrogen-rich gas through directional adjustment of gas flow resistance and maximum pressure difference. The formula for calculating the gas flow resistance of the feed column is: ,in The gas flow resistance coefficient of the feed column when no hydrogen-rich gas is injected (single pulverized coal injection mode) is obtained through experimental measurement or calculation using empirical formulas. The drag adjustment coefficient is obtained by fitting drag coefficient data under different hydrogen-rich gas input rates. This represents the input rate of hydrogen-rich gas. The formula for calculating the maximum pressure difference in the feed column is: ,in The density of the reduced gas is calculated based on the gas composition and the ideal gas law. The gas flow rate is calculated from the incoming gas flow rate and the cross-sectional area of ​​the furnace. The height of the material column, This is the equivalent diameter of the charge column, calculated based on the crucible's inner diameter. Hydrogen-rich gas, by regulating the reduction reaction process, increases the metallization rate of the charge, converting more iron oxides into elemental iron. Simultaneously, it alters the slag's chemical composition (e.g., reducing FeO content, adjusting basicity) and physical properties (e.g., viscosity, surface tension). These changes in slag properties directly affect the pore distribution of the charge layer, increasing porosity and improving pore connectivity, thereby reducing the gas flow resistance of the charge column. ,pass The calculation formula enables directional control of the maximum pressure difference of the feed column, which varies with the amount of hydrogen-rich gas input. The increase, Gradually decrease, It shows a monotonically decreasing trend, and the air permeability of the material column is gradually improving.

[0093] Furthermore, the optimization of the process control scheme takes both kinetic characteristics and droplet performance as dual objectives, and constructs a multi-objective optimization model. The kinetic optimization objective is: ,in As the amount of hydrogen-rich gas input... The changing activation energy of the reaction, through different The following dynamic analysis yielded the following results: This represents the activation energy of the reaction without the injection of hydrogen-rich gas. To optimize the activation energy coefficient, by and The relationship was obtained by fitting; As temperature and The changing reaction rate constant, As the baseline reaction rate constant, For the reaction rate optimization coefficient, through and The relationship was obtained through fitting. The core of kinetic optimization is to minimize the activation energy and maximize the rate constant to improve reduction efficiency. The optimization objective for molten droplet performance is: ,in , Don't follow The varying drip rate and air permeability characteristics, through different The droplet properties were obtained from the following tests. This represents the drip rate without the injection of hydrogen-rich gas. , To optimize the drip rate coefficient, The permeability characteristic value is the value when no hydrogen-rich gas is injected. The permeability optimization coefficients were all obtained through fitting experimental data. The core of droplet performance optimization is to maximize the droplet rate and minimize the permeability characteristic value to improve the permeability of the feed column and the slag-iron separation effect. The NSGA-II multi-objective optimization algorithm was used to solve for the optimal hydrogen-rich gas input. pulverized coal ratio and reduction temperature The objective function of the algorithm is the aforementioned optimization of kinetics and droplet properties, and the constraints include... (hydrogen) or (shale gas) The Pareto optimal solution set is obtained through algorithmic iteration. The parameter combination with the best overall performance is selected as the process control scheme. At the same time, conditions for blocking the formation of harmful phases are set, namely, by controlling the reduction temperature. (≥850℃) and hydrogen-rich gas input range, suppress the formation of Fe3C and TiC, establish a dynamic matching mechanism between hydrogen-rich gas input and pulverized coal injection ratio, and adjust the proportion of furnace hearth gas components in real time to ensure the stability and practicality of the process scheme.

[0094] This implementation optimizes the reducing atmosphere and reaction pathway of vanadium-titanium sinter through hydrogen-rich injection, improving reduction efficiency and metallization, enhancing key droplet temperature parameters and material permeability, and suppressing the formation of harmful phases. This achieves synergistic optimization of reduction performance and droplet characteristics. The process control scheme balances green and low-carbon practices with smooth smelting operations, providing reliable technical support for the industrial application of hydrogen-rich smelting of vanadium-titanium magnetite.

[0095] Based on Example 1, this example details the regulation of hydrogen-rich gas injection on the reduction and droplet properties of vanadium-titanium sinter. The composition of the hearth gas under different injection conditions is determined using energy-mass balance and replacement ratio models. Three types of experiments are designed: hydrogen-pulverized coal composite injection, shale gas-pulverized coal composite injection, and droplet performance testing under different H2 content gradients. Combined with thermogravimetric analysis, XRD detection, SEM characterization, and droplet experimental setup, reduction kinetic data, product phase information, microstructural characteristics, and key droplet parameters are obtained. Specifically:

[0096] This study investigated the regulatory mechanism of hydrogen-rich gas input on the reduction process of vanadium-titanium sinter using hydrogen-pulverized coal composite injection as the core. The experiment fixed the pulverized coal injection ratio at 108 kg / tHM and set three hydrogen injection gradients: 15 kg / tHM (corresponding to hearth gas CO:H2:N2=41:14:45), 30 kg / tHM (CO:H2:N2=36:22:42), and 45 kg / tHM (CO:H2:N2=32:29:39). A single pulverized coal injection mode (CO:H2:N2=47:4:49) served as the control group. The reduction temperatures were selected at two key points: 850℃ and 1000℃, both falling within the second temperature range (T>T). c To avoid the formation of the Fe3C phase.

[0097] Restore weightlessness characteristics by Figure 4 As shown in the diagram, the curve exhibits a three-stage characteristic: slow growth, rapid growth, and then stabilization. In the initial stage of the reaction (0-10 min), the weight loss rate varies little under different gas compositions, all below 8%. After entering the rapid reaction stage (10-40 min), the weight loss rate increases linearly and rapidly, with higher hydrogen content resulting in a steeper curve and a faster rate of weight loss. In the later stage of the reaction (after 40 min), the weight loss rate gradually stabilizes. The weight loss rate under a hydrogen injection rate of 45 kg / tHM is approximately 23% higher than the control group, indicating that the introduction of hydrogen significantly enhances the mass loss process of the reduction reaction and promotes the reduction of iron oxides.

[0098] The evolution of iron reduction degree through Figure 5 Quantitative analysis showed that the reduction rate curves under different gas compositions exhibited the same trend as the weight loss rate curves, and the reduction rate significantly increased with increasing hydrogen injection volume. At 850℃ and 60 min of reaction time, the iron reduction rate of the control group was 78.5%, while the reduction rates of the 15 kg / tHM, 30 kg / tHM, and 45 kg / tHM hydrogen injection gradients reached 83.2%, 87.6%, and 92.3%, respectively. At 1000℃, the reduction rates of each gradient further increased, with the 45 kg / tHM gradient reaching 94.1%, an increase of 15.9% compared to the control group (81.2%), demonstrating that hydrogen injection and temperature increase have a synergistic effect in enhancing reduction.

[0099] The stages and characteristics of reaction rate changes are determined by... Figure 6The curves clearly show two reaction stages. When the reduction progress α < 20%, the first stage occurs, mainly involving the transformation of high-valent iron oxides (Fe2O3, Fe3O4) to low-valent iron oxides (FeO). In this stage, the reduction rates of all gas components are relatively high and the differences are small, with the maximum rate of the 45 kg / t HM hydrogen gradient reaching 0.031 min⁻¹. When α > 20%, the second stage begins, mainly involving the transformation of FeO to elemental Fe. The reduction rate decreases significantly and the differences between gradients widen. The rate of the 45 kg / t HM hydrogen gradient remains at 0.012-0.015 min⁻¹, while the control group only reaches 0.008-0.010 min⁻¹, indicating that hydrogen can still maintain a high rate in the second stage by improving reaction kinetics.

[0100] Fitting and analysis of dynamic parameters are based on Figure 7 Expand on Table 1 (linear fitting results at 850℃) and Table 2 (linear fitting results at 1000℃). Figure 7 (a) and Figure 7 In (b), the scatter points corresponding to each gas composition all exhibit good linear distribution, with a goodness of fit R² all above 0.988, indicating that the ln-ln analysis method can accurately describe the kinetic characteristics of the system. Table 1 shows that at 850℃, the slope (n value) of the control group (S8) is 1.152, and the n values ​​of the hydrogen gradients of 15 kg / tHM (S12), 30 kg / tHM (S13), and 45 kg / tHM (S14) are 1.276, 1.258, and 1.265, respectively, all within the range of 1.2-1.3, corresponding to the reaction mechanism of random nucleation followed by growth; the intercept increases from -3.111 to -2.627 with the increase of hydrogen injection rate, indicating that the reaction rate constant shows an increasing trend.

[0101] Table 1. Linear fitting results of ln(-ln(1-α))-lnt for different reducing gas compositions (hydrogen-pulverized coal composite injection, 850℃)

[0102]

[0103] The data in Table 1 show that increasing the hydrogen injection rate makes the n value closer to the ideal range of the random nucleation and subsequent growth mechanism, with a goodness of fit of over 0.992, indicating that the applicability of this reaction mechanism increases with increasing hydrogen content; the increase in intercept reflects the increase in the reaction rate constant, providing kinetic support for the increase in reduction rate.

[0104] Table 2. Linear fitting results of ln(-ln(1-α))-lnt for different reducing gas compositions (hydrogen-pulverized coal combined injection, 1000℃)

[0105]

[0106] Table 2 shows the fitting results at 1000℃. The n-value for the control group (S15) is 1.245, while the n-values ​​for each hydrogen gradient range from 1.165 to 1.208, consistent with the reaction mechanism of random nucleation followed by growth. The intercept increases significantly with increasing hydrogen injection rate, from -3.355 to -2.187, an increase of 34.8%, indicating that the synergistic effect of temperature increase and hydrogen injection further optimizes the kinetic parameters and improves the reaction rate constant. Calculations using the Arrhenius equation show that the activation energy of the reaction at 1000℃ with a 45 kg / t HM hydrogen gradient is reduced by approximately 25 kJ / mol compared to the control group, while the reaction rate constant is increased by approximately 60%. This fully demonstrates that the hydrogen-coal powder composite injection mode can effectively improve the reduction kinetics of vanadium-titanium sinter.

[0107] To investigate the effect of shale gas-pulverized coal combined injection on the reduction performance of vanadium-titanium sinter, a shale gas-pulverized coal combined injection mode was adopted to explore the influence of the hydrogen-rich atmosphere generated by shale gas cracking on the reduction performance of vanadium-titanium sinter. The experiment maintained a constant pulverized coal injection ratio of 108 kg / tHM and set three shale gas injection gradients: 40 kg / tHM (corresponding to hearth gas CO:H2:N2=43:10:47), 80 kg / tHM (CO:H2:N2=40:15:45), and 120 kg / tHM (CO:H2:N2=37:20:43). A single pulverized coal injection mode (CO:H2:N2=47:4:49) served as the control group. The reduction temperatures were also selected at 850℃ and 1000℃ to ensure comparability with the above experimental conditions.

[0108] Reconstructing the law of weightlessness by Figure 8 As shown, the curve shape is similar to that of the hydrogen-coal powder combined injection mode, but the weight loss rate is slightly lower under the same hydrogen-rich content. Under shale gas gradients of 40 kg / tHM, 80 kg / tHM, and 120 kg / tHM, the weight loss rates after 60 min of reaction were 16.8%, 19.5%, and 22.3%, respectively, which were 10.5%, 28.3%, and 46.7% higher than the control group (15.2%). The reaction completion time (when the weight loss rate tends to stabilize) was 75 min, 61 min, and 53 min, respectively, which were 18.5%, 33.7%, and 42.4% shorter than the control group (92 min). This indicates that increasing the shale gas injection rate can continuously enhance the reduction weight loss process, and the regulation effect has good linear characteristics.

[0109] The evolution of iron reduction degree is characterized by... Figure 9As shown, the reduction degree increases stepwise with the increase of shale gas injection rate. At 850℃ and 60 min, the reduction degree of the control group was 78.5%, while the reduction degrees of the 40 kg / tHM, 80 kg / tHM, and 120 kg / tHM shale gas gradients were 81.3%, 85.7%, and 88.7%, respectively. At 1000℃, the reduction degrees of each gradient further increased to 83.5%, 87.9%, and 91.2%, which were 2.8%, 8.2%, and 12.3% higher than the control group (81.2%), respectively. Compared with Example 1, it can be seen that under the same H2 volume ratio, the reduction degree of the shale gas gradient is slightly lower than that of the hydrogen gradient (about 2-3 percentage points). This is because the CH4 cracking in the shale gas consumes some energy, resulting in a slight decrease in the reduction efficiency of H2, but overall it is still significantly better than the single coal injection mode.

[0110] The stage characteristics of reaction rate are obtained through Figure 10 As shown, the process also exhibits a two-stage characteristic. When the reduction progress α < 20%, it is in the first stage, with relatively high reduction rates for each gradient. The maximum rate of the 120 kg / tHM shale gas gradient reaches 0.028 min⁻¹, slightly lower than the 45 kg / tHM hydrogen gradient (0.031 min⁻¹). When α > 20%, it enters the second stage, with the rate of the 120 kg / tHM shale gas gradient maintained at 0.010-0.013 min⁻¹, higher than the control group (0.008-0.010 min⁻¹). Moreover, the rate of the second stage steadily increases with the increase of shale gas injection volume, indicating that the H2 produced by shale gas cracking can effectively participate in the reduction reaction of low-valent iron oxides, maintaining a high rate.

[0111] The fitting results of the dynamic parameters are based on Figure 11 The results are expanded from Table 3 (linear fitting results at 850℃) and Table 4 (linear fitting results at 1000℃). Figure 11 (a) and Figure 11 In (b), the scatter plots of each shale gas gradient show good linear distribution, with a goodness of fit R² all above 0.984, proving that the ln-ln analysis method is also applicable to this system. Table 3 shows that at 850℃, the n value of the control group (S8) is 1.152, and the n values ​​of the shale gas gradients of 40kg / tHM (S9), 80kg / tHM (S10), and 120kg / tHM (S11) are 1.318, 1.231, and 1.181, respectively, all within the range of 1.18-1.32, corresponding to the reaction mechanism of random nucleation followed by growth; the intercept increases from -3.398 to -2.951 with the shale gas injection rate, reflecting a gradual increase in the reaction rate.

[0112] Table 3. Linear fitting results of ln(-ln(1-α))-lnt for different reducing gas compositions (shale gas-pulverized coal combined injection, 850℃)

[0113]

[0114] The data in Table 3 show that when the shale gas injection rate is moderate (80 kg / tHM), the n value is closer to the ideal range, the goodness of fit reaches 0.996, and the kinetic characteristics are more stable. The overall upward trend of the intercept indicates that shale gas injection can effectively increase the reaction rate constant and enhance the reduction reaction kinetics.

[0115] Table 4. Linear fitting results of ln(-ln(1-α))-lnt for different reducing gas compositions (shale gas-pulverized coal combined injection, 1000℃)

[0116]

[0117] Table 4 shows the fitting results at 1000℃. The n-value for the control group (S15) is 1.245, while the n-values ​​for each shale gas gradient range from 1.103 to 1.280, still conforming to the random nucleation followed by growth mechanism. The intercept increases from -3.186 to -2.264 with increasing shale gas injection rate, an increase of 29.0%, indicating that higher temperatures can further amplify the regulation effect of shale gas. Calculations based on the Arrhenius equation show that the activation energy of the 120 kg / tHM shale gas gradient at 1000℃ is approximately 20 kJ / mol lower than the control group, and the reaction rate constant is increased by approximately 45%. Although this is lower than the increase in the hydrogen-coal powder combined injection mode, it is still significantly better than the single coal injection mode, proving that the shale gas-coal powder combined injection mode also possesses the technical effect of optimizing reduction kinetics.

[0118] The effect of hydrogen-rich injection on the droplet properties of vanadium-titanium sinter was investigated. The control mechanism of hydrogen-rich injection on the droplet properties of vanadium-titanium sinter was studied. Five reducing atmospheres were set up in the experiment (corresponding to No.1-No.5 in Table 5). No.1 was the control group (30%CO+70%N2), and No.2-No.5 were hydrogen-rich atmospheres (H2 content gradually increased). The pulverized coal injection ratio was fixed at 108 kg / tHM, and the reduction temperature was 1000℃. The effect of H2 content on key droplet parameters was explored through the droplet experimental system.

[0119] The evolution of the critical temperature of the molten droplet is determined by... Figure 12 As shown, Figure 12 include Figure 12 (a)- Figure 12 (e) Five subplots and corresponding experimental data plots for groups No.1-No.5, Figure 12 (f) is a summary comparison chart of the key temperatures in the five groups of molten droplet experiments (a)-(e), combined with a comprehensive analysis of Table 5: Figure 12 (a)- Figure 12 (e) The sub-figures sequentially present the shrinkage rate-temperature curves and pressure difference-temperature curves of the furnace charge under five different H2 content atmospheres. Among them, the shrinkage rate curve shows that the softening initiation temperature T10 (Shrinkage rate up to 10%) From No. 2 ( Figure 12 b) dropped steadily from 1092℃ to No.4 ( Figure 12 d) 1080℃, then slightly increased to No.5 ( Figure 12 e) 1081℃, with an overall fluctuation of only 12℃; softening final temperature T 40 (Shrinkage rate reaches 40%) in No. 3 ( Figure 12 c) dropped to a low of 1231℃ and then gradually rose again, No. 5 ( Figure 12 e) reaches 1262℃, making the softening range ΔT1(T 40 -T 10 The temperature increased from 149℃ in No. 2 to 181℃ in No. 5, an increase of 21.5%, demonstrating that the hydrogen-rich atmosphere made the softening process of the furnace charge more dispersed. The pressure difference curve combined with key temperature data shows that the melting initiation temperature T_S (the temperature at which the pressure difference reaches 0.5 kPa) increases significantly with increasing H2 content, from No. 2 (… Figure 12 b) The temperature steadily rose from 1282℃ to No. 5. Figure 12 e) reached 1369℃, an increase of 6.8%; dripping temperature T d In No.4 ( Figure 12 After rising to a maximum of 1534℃ in d), No. 5 ( Figure 12 e) drops to 1512℃, causing the droplet temperature range ΔT2(T) to decrease. d -T S The temperature range showed a trend of first increasing and then decreasing, from 194℃ for No. 2 to 220℃ for No. 3 and then decreasing to 143℃ for No. 5. This reflects that excessively high H2 content will shorten the temperature range from melting to dripping, while No. 1 ( Figure 12 a) The temperature parameters of the control group and the hydrogen-rich group were significantly different. 10 The highest temperature (1147℃) and the narrowest ΔT1 (105℃) further confirm the directional control effect of hydrogen-rich atmosphere on the temperature characteristics of furnace charge droplets.

[0120] Table 5 Results of the molten drop experiment

[0121]

[0122] Table 5 clearly demonstrates the directional control effect of hydrogen-rich atmosphere on the critical temperature of the melting droplet. Compared with the control group, hydrogen-rich atmosphere resulted in T... 10 On average, the temperature drops by about 60°C. SThe average temperature increased by about 50°C, and ΔT1 increased significantly. This is closely related to the fact that hydrogen reduction changes the phase composition of the furnace charge, reduces the initial softening temperature, and increases the melting temperature. At the same time, the maximum pressure difference ΔPm decreased from 34.11 kPa to 19.97 kPa with the increase of H2 content, a decrease of 41.4%. The characteristic value of air permeability SD continued to decrease from 3809.33 kPa·°C to 630.94 kPa·°C, a decrease of 83.4%, indicating that hydrogen-rich injection can significantly improve the air permeability of the charge column.

[0123] The air permeability and dripping characteristics of the material column are determined by... Figure 13 (The total characteristic value curves under reducing gas with different H2 ratios) further verify that as the H2 content increases, the peak value of the pressure difference curve gradually decreases, and the temperature point at which the peak value appears gradually shifts later, indicating that the hydrogen-rich atmosphere can delay the blockage of the column pores and reduce the gas flow resistance. Referring to Table 5, when the H2 content is 15% (No. 4), the drip rate reaches its maximum value of 51.59%, an increase of 13.7% compared to the control group (45.39%). At this point, the SD is only 1174.71 kPa·℃, and the column permeability and slag-iron separation effect reach their optimal levels. As the H2 content continues to increase (No. 5), the drip rate decreases slightly, but the SD continues to decrease, further improving the column permeability.

[0124] The composition and phase characteristics of the dripping slag are shown in Table 6 (Composition of dripping slag) and Figure 14 The phase composition analysis of the dripping slag under different H2 ratios in the reducing gas was performed. Table 6 shows that the contents of CaO, MgO, SiO2, Al2O3, and TiO2 in the dripping slag did not change significantly, but the contents of TFe (MFe, FeO) changed significantly, first decreasing from 36.80% in No.2 to 17.83% in No.4, and then increasing to 25.39% in No.5. The TFe content in No.4 was the lowest among all groups, indicating that the slag-iron separation effect was the best at this time, which is consistent with the result of the maximum dripping rate. The quaternary basicity R4 gradually decreased from 1.25 to 0.99 with the increase of H2 content, indicating that the hydrogen-rich atmosphere would slightly reduce the basicity of the dripping slag.

[0125] Table 6. Composition of dripping residue

[0126]

[0127] Figure 14The XRD patterns showed that the main phases of the dripping slag under various atmospheres were magnesia (Ca2MgSi2O7, melting point 1450℃) and perovskite (CaTiO3, melting point 1420℃), with a small amount of metallic iron. The H2 content had little effect on the phase type, but a significant effect on the diffraction peak intensity. In No.4 (H2 content 15%), the diffraction peak intensity of magnesia was the highest, while the diffraction peak intensity of perovskite was relatively low. The low melting point of magnesia is beneficial to reducing slag viscosity and promoting slag-iron dripping and separation. This is consistent with the results in Tables 5.6 and 5.7, further verifying that the dripping performance is optimal when the H2 content is 15%.

[0128] The evolution law of slag phase is obtained through Figure 15 (The phase diagram of SiO2-CaO-MgO-(Al2O3-TiO2)) aids analysis, showing that point O1 represents the initial composition of the slag phase after complete iron reduction. During cooling, CaTiO3 precipitates along the O1→O2 path, eutecticly crystallizing with Mg2SiO4 at point O2, and forming a ternary eutectic phase of CaTiO3, Mg2SiO4, and CaAl2SiO8 at point O3. A hydrogen-rich atmosphere slightly shifts the position of point O1 by altering the TFe content and basicity of the dripping slag, but does not change the main crystallization path of the slag phases, only affecting the relative content of each phase. This explains why the H2 content has a relatively small impact on the phase types of the dripping slag.

[0129] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any changes, modifications, substitutions, integrations, and parameter changes made to these embodiments within the spirit and principles of the present invention, without departing from the principles and spirit of the present invention, through conventional substitutions or to achieve the same function, fall within the scope of protection of the present invention.

Claims

1. A method for improving the reducing and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection, characterized in that, include: Determine the core characteristic parameters of vanadium-titanium sinter and the parameters of the blast furnace injection system. The core characteristic parameters include chemical composition, phase composition and pore structure, while the injection system parameters cover hydrogen-rich gas type, injection gradient, hearth gas composition control target and reduction temperature system. A multi-mode injection system is constructed, which forms a differentiated injection system by combining hydrogen-rich gas and pulverized coal. The amount of hydrogen-rich gas input is adjusted based on the injection gradient to control the proportion of reducing gas components in the hearth gas. Isothermal reduction experiments of vanadium-titanium sinter were carried out under the reduction temperature system. Combined with thermogravimetric analysis, phase detection and micro-characterization techniques, data on the reduction reaction process, product phase information and microstructure characteristics were obtained. A kinetic analysis model was constructed based on the reduction reaction process data. The reaction mechanism and kinetic parameters were determined by fitting characteristic functions, and a correlation mechanism between the amount of hydrogen-rich gas input and the reduction reaction process was established. Design a gradient hydrogen content experimental scheme, conduct vanadium-titanium sinter droplet performance tests, obtain key temperature correlation data of droplets and air permeability data of material columns, and construct the correspondence between hydrogen content and droplet characteristics. Based on the correlation mechanism and corresponding relationship, the injection mode, hydrogen-rich gas input and reduction temperature parameters are optimized to form a process control scheme for the targeted improvement of the reduction droplet properties of vanadium-titanium sinter.

2. The method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection according to claim 1, characterized in that, The multi-element injection mode includes single pulverized coal injection mode, hydrogen-pulverized coal composite injection mode, and shale gas-pulverized coal composite injection mode. The single pulverized coal injection mode maintains the volume ratio of CO, H2, and N2 in the hearth gas within a preset baseline range by fixing the pulverized coal injection parameters; The hydrogen-pulverized coal composite injection mode adjusts the input amount according to the increasing hydrogen-rich gas injection gradient, and simultaneously realizes the dynamic adaptation of CO volume ratio, H2 volume ratio, and N2 volume ratio. The shale gas-pulverized coal composite injection mode is based on the inherent component characteristics of shale gas. It adjusts the input amount according to the injection gradient to achieve step-by-step control of the volume ratio of the three gases in the hearth gas.

3. The method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection according to claim 1, characterized in that, The reduction temperature system is divided into two different temperature ranges by a temperature critical value. Determined through calculations using thermodynamic equilibrium equations: ,in This refers to the enthalpy change of the secondary reaction between the reducing gas and the reduction product. This represents the entropy change of the reaction. This is the critical temperature value; When the reduction temperature At this time, the first temperature range that triggers the secondary reaction is formed; When the reduction temperature At that time, a second temperature range is formed that blocks the secondary reaction.

4. The method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection according to claim 1, characterized in that, The construction of the kinetic analysis model includes reaction progress quantification, mode function matching, and kinetic parameter calculation, specifically: reaction progress pass Quantification, among which For a specific time Actual weight loss under the conditions This represents the theoretical maximum weight loss. Construct using feature function fitting method and The linear relationship is shown in the fitted equation as follows: ,in Let A be the characteristic constant of the reaction, E be the pre-exponential factor, R be the activation energy of the reaction, and T be the gas constant. Reaction time; Based on the numerical distribution range of the reaction characteristic constant n, the reduction reaction mechanism type is determined and the corresponding reaction mode function is matched. ; Reaction rate constant Following the Arrhenius equation The reduction reaction rate is determined by the fundamental kinetic equation. calculate.

5. The method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection according to claim 4, characterized in that, The stages of a reduction reaction are determined by the reaction progress threshold. Define and satisfy: ,in The theoretical weight loss for the complete reduction of high-valence iron oxides to low-valence iron oxides; when At that time, the reaction system is in the first stage of the transformation from high-valence iron oxide to low-valence iron oxide; when At that time, the reaction system is in the second stage of the transformation of low-valent iron oxides into elemental iron.

6. The method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection according to claim 1, characterized in that, In the droplet performance test, the shrinkage rate of the furnace charge was used as a measure. Pressure difference with the material column Dynamic monitoring data, combined with the following correlation formula, are used to obtain the critical temperature correlation data of the molten droplet: in The initial shrinkage rate, The temperature coefficient of shrinkage. Reference temperature; ,in The initial pressure difference, This is the temperature coefficient of pressure difference; By solving and The corresponding temperature values ​​yielded the softening initiation temperature, softening termination temperature, and melting initiation temperature. Combined with the monitoring temperature of the first drop of slag and iron, key temperature correlation data were formed. , To preset the shrinkage rate threshold, This is the preset differential pressure threshold.

7. The method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection according to claim 6, characterized in that, In the droplet performance test, the droplet rate and air permeability characteristic value are calculated simultaneously. The calculation method is as follows: drip rate pass Calculation, where The total mass of the dripping slag and iron. This refers to the total mass of vanadium-titanium sinter used in the experiment; Breathability characteristic value SD passed Calculation, where To soften the initial temperature, The dripping temperature, The pressure difference of the material column at temperature T.

8. The method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection according to claim 1, characterized in that, The correlation analysis between the phase and microstructure of the reduction products satisfies: Degree of phase transformation ,in , , , The diffraction intensities of elemental Fe and iron oxides in various valence states are respectively. Microstructure evolution characteristics are characterized by grain refinement coefficient Quantification, among which The average grain size when no hydrogen-rich gas was injected. The average grain size after hydrogen-rich gas injection; Establish , With hydrogen-rich gas input Relationship: , where a, b, c, and d are the fitting coefficients.

9. The method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection according to claim 1, characterized in that, The effect of hydrogen-rich gas on the permeability of the feed column satisfies the following relationship: Gas flow resistance of the material column ,in This represents the drag coefficient when no hydrogen-rich gas is injected. This is the resistance adjustment coefficient; Maximum pressure difference of the material column ,in For the density of coal gas, The gas flow rate is the gas flow rate. The height of the material column, The equivalent diameter of the material column; By adjusting the amount of hydrogen-rich gas input ,accomplish Targeted regulation.

10. The method for improving the reduction and dripping properties of vanadium-titanium sinter based on hydrogen-rich gas injection according to claim 1, characterized in that, The optimization of the process control scheme satisfies: kinetic optimization objective: ,in The activation energy varies with the amount of hydrogen-rich gas input Q. The reaction rate constant varies with temperature T and Q. , For each optimization coefficient; Optimization goals for molten droplet performance: ,in , They are respectively The changing drip rate and air permeability characteristic values, , , For each performance optimization coefficient; The optimal hydrogen-rich gas input was determined using a multi-objective optimization algorithm. pulverized coal ratio and reduction temperature .

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