A low-carbon smelting method for blast furnace based on slag system reconstruction

Abstract

The present application provides a kind of based on slag series reconstruction's blast furnace low carbon smelting method, it is related to the technical field of steel metallurgy.The present application method specifically includes: first, by controlling the binary basicity R2 of final slag ≥1.25, and corresponding adjustment MgO content, the viscosity of final slag at 1500 DEG C high temperature is optimized ≤0.35Pa·s;Second, deduce initial slag composition and ensure melting point ≥1400 DEG C, unit iron yield initial slag heat storage capacity ≥62940kJ;Third, by rich oxygen rate is promoted to 24% and above guarantee tuyere theoretical combustion temperature ≥2350 DEG C, to match the high temperature heat demand of increasing melting point due to slag series basicity oxide increase;Finally, dynamic correction slag series setting and charge matching, realize the closed loop control of slag performance.The present application realizes the system improvement of blast furnace gas permeability, liquid permeability and thermal efficiency, thereby reduce blast furnace fuel consumption and carbon emission.

Description

Technical Field

[0001] This invention relates to the technical field of iron and steel metallurgy, and in particular to a low-carbon blast furnace smelting method based on slag system reconstruction, which is used to reduce blast furnace carbon emissions and improve smelting efficiency, and belongs to the field of metallurgical process optimization and energy conservation and emission reduction technology. Background Technology

[0002] The steel industry is a major carbon emitter, especially the long-process steelmaking system based on blast furnaces and converters, which accounts for the highest proportion of carbon emissions. As a core unit in the steelmaking process, the fuel consumption and CO2 emissions of the blast furnace smelting process have received significant attention. Traditional blast furnace operation mainly focuses on controlling thermal regimes such as fuel ratio, blast temperature, and oxygen enrichment rate. However, practical experience with "seven-tenths slag formation" shows that the design of the blast furnace slag system directly affects slag-iron fluidity, softening zone structure, and thermal efficiency, and is key to further reducing carbon emissions.

[0003] In traditional blast furnace smelting, the binary basicity (CaO / SiO2) of the final slag is typically controlled within the range of 1.0-1.2, mainly due to two constraints: first, sulfur (S) in the molten iron needs to be removed through alkaline slag to avoid affecting the performance of the steel; second, harmful elements such as alkali metals (K, Na) in the furnace charge need to be discharged through the slag. If the basicity is too high, it will lead to insufficient alkali removal capacity and problems such as furnace wall nodule formation. However, the viscosity of the final slag within this basicity range is generally high (>0.5 Pa·s) at a high temperature of 1500℃. Especially when the Al2O3 content is high (>15%), the slag fluidity is further deteriorated, resulting in increased slag-iron retention, increased resistance in the softening zone, and consequently, a higher fuel ratio.

[0004] For example, Chinese patent CN117604175A discloses a blast furnace smelting method using low-grade raw materials. This method involves changing the material distribution and vibration methods, reducing the air inlet area, controlling the cooling water volume, increasing the slag volume to improve the slag erosion resistance of the taphole clay and main channel refractory, shortening the tapping interval, increasing the drill bit diameter used in the tapping machine, and adjusting production parameters to adapt to the production changes caused by the decrease in the grade of the slag. Specifically, it adjusts the binary basicity and quaternary basicity of the slag, the hot blast pressure, and the oxygen enrichment. Clearly, this adjustment method requires multi-faceted coordinated regulation, involving many aspects and numerous adjustments. While it does improve slag fluidity and facilitates slag and iron removal, the process is long and complex, with high operational difficulty. It involves adjusting the binary basicity and oxygen enrichment of the slag, but the range of adjustment for the binary basicity is relatively limited, and adjusting the oxygen enrichment reduces the oxygen enrichment, thereby reducing output.

[0005] Chinese patent CN119320850A discloses a blast furnace slagging system based on magnesium-aluminum ratio optimization. This system determines the cause of incomplete magnesium-aluminum reaction within the blast furnace by combining abnormal oxygen concentration and magnesium-aluminum ratio, and promptly replenishes the blast furnace with oxygen or magnesium-aluminum solids, thus providing accurate online monitoring and stabilizing the magnesium-aluminum reaction within the blast furnace, thereby improving blast furnace stability and metal recovery rate. However, while this method optimizes the blast furnace slagging system and employs magnesium-aluminum ratio and oxygen optimization, it does not consider the synergistic effect of binary alkaline slag and oxygen enrichment on the combination of high-melting-point, high-energy-carrying initial slag and low-viscosity final slag.

[0006] In addition, traditional slag system design is dominated by "passive alkali removal", and the initial slag melting point is relatively low (usually <1400℃). It is difficult to form a stable high-temperature heat storage layer in the softening zone, which aggravates the heat load fluctuation in the lower part of the blast furnace and restricts the realization of low-carbon smelting.

[0007] Chinese patent CN114662767A discloses a method and system for controlling the cost of low-carbon blast furnace smelting. This method first acquires fuel cost data for low-carbon blast furnace smelting, then establishes a smelting cost objective function, next obtains the constraints of low-carbon blast furnace smelting and the matching fuel ratio range, then calculates the minimum cost value for smelting a preset quantity of steel, and finally obtains the fuel ratio at the minimum cost value. Clearly, although it is possible to obtain the fuel ratio at the minimum cost value by establishing an objective function from data, this method is not suitable for low-carbon blast furnace smelting methods involving slag system reconstruction.

[0008] Therefore, there is an urgent need for a slag system reconstruction method with multi-parameter synergistic control, which can achieve a dynamic balance between high energy storage and high-melting-point primary slag and low viscosity final slag through a composite approach of "high basicity + high MgO + high oxygen enrichment", providing a new path for low-carbon smelting in blast furnaces. Summary of the Invention

[0009] The main objective of this invention is to solve the technical problems existing in the prior art, including: 1) the contradiction of sacrificing fluidity to ensure alkali removal capacity in traditional slag systems; 2) the problem of excessive viscosity of blast furnace final slag leading to deterioration of liquid permeability and air permeability; 3) the problem of low melting point of initial slag, insufficient heat storage capacity of the softening zone, and unstable temperature field; 4) the problem that existing technologies have single adjustment parameters or poor coordination, making it difficult to systematically optimize slag-iron flow and thermal efficiency, resulting in limited carbon reduction potential.

[0010] Therefore, a low-carbon smelting method for blast furnaces based on slag system reconstruction is proposed to solve the aforementioned problems. The core idea is to construct a slag system of "high melting point and high energy carrying initial slag + low viscosity final slag" under the guidance of the phased slag system design concept. By using high basicity and high MgO control methods, and combining high oxygen-enriched blast to provide smelting heat support, the permeability, liquid permeability and thermal efficiency of the blast furnace are systematically improved, thereby reducing blast furnace fuel consumption and carbon emissions.

[0011] A blast furnace low-carbon smelting method based on slag system reconstruction, the method comprising the following steps:

[0012] S1. Slag System Basic Parameter Design Stage: It is necessary to optimize the final slag viscosity and select the final slag components based on the optimized final slag viscosity to construct a slag system with "low viscosity final slag" corresponding to the final slag viscosity and final slag components; then, the initial slag components are back-inferred and the performance is evaluated based on the slag system with "low viscosity final slag".

[0013] S2. Thermodynamic matching stage: Temperature field coordination is carried out based on the initial slag composition - the melting point and heat storage capacity of the initial slag are calculated to obtain the melting point of the initial slag. At the same time, the heat storage capacity of the slag required per unit iron production is evaluated. The required heat storage capacity of the slag meets the requirements to ensure the stability of the temperature field in the blast furnace softening zone. Then, the heat compensation stage is carried out - high oxygen enrichment blast. The oxygen enrichment rate of the high oxygen enrichment blast needs to meet the requirement of increasing the theoretical combustion temperature of the tuyeres to meet the high temperature heat intensity.

[0014] S3. Construction of dynamic control system: Based on the analysis of the final slag composition and the results of viscosity measurement, the design of the basic parameters of the slag system and the thermodynamic matching stage are dynamically corrected to ultimately achieve closed-loop control of slag performance.

[0015] Optionally, the viscosity of the final slag after optimization design in S1 is not higher than 0.35 Pa·s at 1500℃, and the binary basicity R of the "low viscosity final slag" is not lower than 1.25.

[0016] Optionally, the viscosity of the final slag can be reduced in S1 by increasing the binary basicity R=CaO / SiO2 and increasing the MgO content.

[0017] Optionally, the slag system construction method of "low viscosity final slag" in S1 is to select different combinations of binary basicity R=CaO / SiO2, Al2O3 mass fraction, and MgO content based on the actual operation of the blast furnace, measure and construct a slag viscosity database, and screen out slag combinations with viscosity not higher than 0.35 Pa·s at a high temperature of 1500℃ as target final slag components to construct the slag system of "low viscosity final slag".

[0018] Optionally, in S1, based on the final slag setting, and combining the ash composition of coke and pulverized coal, the furnace charge structure, and operating parameters, including coke ratio, coal ratio, and slag-iron ratio, the content of major oxides in the initial slag, including the content of CaO, SiO2, MgO, and Al2O3, is deduced. The FeO content needs to be set to 25%, and a model for deducing the initial slag is established based on material balance.

[0019] Optionally, the melting point of the primary slag in S2 shall not be lower than 1400℃, and the slag heat storage required per unit ton of iron production shall not be lower than 62940kJ.

[0020] Optionally, the oxygen enrichment rate of the high oxygen-enriched blast in S2 needs to be set to no less than 24%, the theoretical combustion temperature of the tuyeres needs to be increased to no less than 2350℃, and the high temperature heat intensity requirement needs to reach the minimum temperature at which the high melting point slag system can melt and the slag superheat is 70±10℃.

[0021] Optionally, the fuel ratio that ultimately achieves closed-loop control of slag performance in S3 can be reduced by 8-15%, and carbon emissions per ton of iron can be reduced by 2-4%.

[0022] Optionally, the blast furnace low-carbon smelting method based on slag system reconstruction can be used for effective volumes greater than 1000m³. From the adjustment of start-up parameters to the new slag system reaching stable performance, a transition period of about 5-7 days, or 120-168 hours, is required.

[0023] Optionally, the blast furnace low-carbon smelting method based on slag system reconstruction can be used in modern ironmaking blast furnaces with an effective volume of 2000 m³ or more.

[0024] Technical principle of the invention:

[0025] With the popularization of refined feedstock technology, the load of harmful elements in the furnace charge has been significantly reduced, and the traditional "high alkali discharge requirement" has gradually weakened its constraints on the slag system. At the same time, the large-scale development of modern blast furnaces has placed higher demands on the physical properties of slag (such as high-temperature fluidity and thermal stability).

[0026] The inventors found that while simply increasing alkalinity can improve desulfurization, it can also lead to an increase in the melting point of the slag. If there is insufficient heat compensation (such as high oxygen-enriched blast), it can easily cause slag buildup in the hearth. On the other hand, relying solely on MgO adjustment can broaden the low viscosity temperature range of the slag, but excessive MgO (>12%) will reduce the heat capacity of the slag.

[0027] This invention overcomes traditional basicity limitations by reconstructing the slag system composition. Utilizing the synergistic effect of high basicity (R² ≥ 1.25) and high MgO, it significantly reduces the viscosity of the final slag at 1500℃ (≤ 0.35 Pa·s) while ensuring desulfurization capacity. Furthermore, it constructs a "high-melting-point (≥ 1400℃) initial slag" to form a high-energy-carrying buffer layer in the softening zone, enhancing the furnace belly heat reserve. Combined with the low-viscosity final slag, this ensures efficient slag-iron separation, thereby systematically optimizing the blast furnace's permeability and thermal efficiency. This slag system optimization approach, by reducing the final slag viscosity while ensuring the initial slag's heat storage capacity, provides a new breakthrough for low-carbon blast furnace smelting.

[0028] Furthermore, based on the above, it is also necessary to combine high-oxygen-enriched blast to provide smelting heat support and construct a slag system of "high-melting-point, high-energy-carrying initial slag + low-viscosity final slag" to achieve a systematic improvement in blast furnace permeability, liquid permeability and thermal efficiency, thereby reducing blast furnace fuel consumption and carbon emissions.

[0029] The above technical solution has at least the following advantages compared with the existing technology:

[0030] The above-mentioned solution, proposed by this invention, is a low-carbon smelting method for blast furnaces based on slag system reconstruction, which can solve the technical problems existing in the prior art, including: 1) the contradiction of traditional slag systems sacrificing fluidity to ensure alkali removal capacity; 2) the problem of excessively high viscosity of blast furnace final slag leading to deterioration of liquid permeability and air permeability; 3) the problem of low melting point of initial slag, insufficient heat storage capacity of the softening zone, and unstable temperature field; 4) the problem that existing technologies have single adjustment parameters or poor coordination, making it difficult to systematically optimize slag-iron flow and thermal efficiency, resulting in limited carbon reduction potential.

[0031] This invention designs basic slag parameters and selects different combinations of binary basicity (R=CaO / SiO2), Al2O3 mass fraction, and MgO content based on the actual operation of the blast furnace. It then measures and constructs a slag viscosity database and screens out slag combinations with a viscosity ≤0.35 Pa·s at 1500℃ as the target final slag composition.

[0032] This invention constructs a slag system with "low viscosity final slag," and by controlling the binary basicity and magnesium oxide content while reducing the final slag viscosity, it obtains a primary slag composition content that can improve the heat reserve of the furnace belly. Furthermore, based on a material balance-based model for inferring the primary slag composition, the obtained primary slag composition content has a small deviation, reducing the number of dynamic adjustments required. Specifically, it includes the following superior effects:

[0033] 1) Coordination between upper and lower parts, and consideration of functions: Starting with "low viscosity final slag", the primary slag with "high melting point and high heat storage" characteristics was designed in reverse through the synergistic regulation of alkalinity and MgO. For the first time, the contradiction between the fluidity of the lower part of the blast furnace and the thermal stability of the middle part was solved in the same slag system.

[0034] 2) Storing heat and ensuring stable operation: The high heat storage slag obtained forms an effective heat buffer zone in the softening zone, which enhances the stability of the thermal regime in the upper part of the blast furnace, improves the overall resistance to fluctuations of the blast furnace, and provides a reliable guarantee for the implementation of low-carbon and high-intensity smelting.

[0035] This invention, through temperature field coordination—calculation of initial slag melting point and heat storage capacity—enables the simultaneous calculation of the initial slag melting point using a multi-dimensional slag thermophysical property database and the assessment of the slag heat storage required per unit of iron production, thereby ensuring the stability of the temperature field in the blast furnace softening zone. Specifically, it offers the following superior effects:

[0036] 1) Quantitative design: The abstract concept of thermal stability of the soft melting zone is transformed into two core thermal parameters that can be accurately calculated and set: "initial slag melting point" and "heat storage per ton of iron".

[0037] 2) Synergistic buffering: The high melting point ensures the mechanical stability of the softening zone structure, while the high heat storage capacity provides a strong temperature buffering capability. The two work together to effectively suppress thermal fluctuations in the middle of the blast furnace.

[0038] 3) Support enhancement: This step ensures the smooth operation of the blast furnace from a thermal perspective, and provides the necessary thermal stability conditions for the safe implementation of enhanced smelting and carbon reduction measures such as "high oxygen enrichment, high alkalinity, and low viscosity".

[0039] This invention employs a thermal compensation stage—high-oxygen-enriched blast—to further increase the theoretical combustion temperature at the tuyeres by controlling the oxygen enrichment rate, thereby meeting the high-temperature thermal intensity requirements. The high-temperature thermal intensity requirement is to reach the minimum temperature at which the high-melting-point slag system can melt, with a slag superheat of 70±10℃.

[0040] This invention can dynamically correct the slag system settings and furnace charge matching based on online final slag composition analysis and viscosity measurement results, making the obtained results accurate and efficient, and easy to apply in industry; at the same time, it can realize closed-loop control of slag performance to reduce preparation costs, improve preparation efficiency, control carbon emissions, and be environmentally friendly.

[0041] In summary, compared with traditional blast furnace ironmaking, the method of this invention reconstructs the slag system through the optimization design of the final slag viscosity in the design of the basic parameters of the slag system, the back-inference and performance evaluation of the slag composition, the coordination of the temperature field with thermodynamic matching, the calculation of the initial slag melting point and heat storage capacity and the heat compensation stage, the high oxygen enrichment blast, and the construction of a dynamic control system. This method is simple and easy to operate, with multi-parameter coordinated control. The technical approach overcomes the technical prejudice that "the basicity of traditional blast furnace smelting cannot be too high, which will reduce the viscosity of the molten slag and lead to many technical problems, including slag and iron sticking and blockage, and unstable temperature field in the blast furnace softening zone." The slag system reconstruction has high accuracy, is environmentally friendly, low cost and high efficiency, and is conducive to large-scale industrial production and application. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 This is a process flow diagram of a blast furnace low-carbon smelting method based on slag system reconstruction according to the present invention. Detailed Implementation

[0044] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0045] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0046] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0047] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0048] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0049] A blast furnace low-carbon smelting method based on slag system reconstruction, wherein the blast furnace low-carbon smelting method based on slag system reconstruction combines Figure 1 Includes the following steps:

[0050] S1. Slag System Basic Parameter Design Stage: It is necessary to optimize the final slag viscosity and select the final slag components based on the optimized final slag viscosity to construct a slag system with "low viscosity final slag" corresponding to the final slag viscosity and final slag components; then, the initial slag components are back-inferred and the performance is evaluated based on the slag system with "low viscosity final slag".

[0051] S2. Thermodynamic matching stage: Temperature field coordination is carried out based on the initial slag composition - the melting point and heat storage capacity of the initial slag are calculated to obtain the melting point of the initial slag. At the same time, the heat storage capacity of the slag required per unit iron production is evaluated. The required heat storage capacity of the slag meets the requirements to ensure the stability of the temperature field in the blast furnace softening zone. Then, the heat compensation stage is carried out - high oxygen enrichment blast. The oxygen enrichment rate of the high oxygen enrichment blast needs to meet the requirement of increasing the theoretical combustion temperature of the tuyeres to meet the high temperature heat intensity.

[0052] S3. Construction of dynamic control system: Based on the analysis of the final slag composition and the results of viscosity measurement, the design of the basic parameters of the slag system and the thermodynamic matching stage are dynamically corrected to ultimately achieve closed-loop control of slag performance.

[0053] Specifically, the viscosity of the final slag after optimization design in S1 is not higher than 0.35 Pa·s at 1500℃, and the binary basicity R of the "low viscosity final slag" is not lower than 1.25.

[0054] In particular, the viscosity of the final slag is reduced in S1 by increasing the binary basicity R=CaO / SiO2 and increasing the MgO content.

[0055] Specifically, the slag system construction method of "low viscosity final slag" in S1 is based on the actual operation of the blast furnace. Different combinations of binary basicity R=CaO / SiO2, Al2O3 mass fraction, and MgO content are selected. A slag viscosity database is measured and constructed. Slag combinations with viscosity not higher than 0.35 Pa·s at 1500℃ are selected as target final slag components to construct the slag system of "low viscosity final slag".

[0056] Specifically, in S1, based on the final slag setting, and combined with the ash composition of coke and pulverized coal, the furnace charge structure and operating parameters, including coke ratio, coal ratio, and slag-iron ratio, the content of major oxides in the initial slag, including the content of CaO, SiO2, MgO, and Al2O3, is deduced. The FeO content needs to be set to 25%, and a model for deducing the initial slag is established based on material balance.

[0057] Specifically, the melting point of the primary slag in S2 is not lower than 1400℃, and the slag heat storage required per unit ton of iron production is not lower than 62940kJ.

[0058] Specifically, the oxygen enrichment rate of the high oxygen-enriched blast in S2 needs to be set to no less than 24%, the theoretical combustion temperature of the tuyeres needs to be increased to no less than 2350℃, and the high temperature heat intensity requirement is to reach the minimum temperature at which the high melting point slag system can melt and the slag superheat is 70±10℃.

[0059] In particular, the fuel ratio that ultimately achieves closed-loop control of slag performance in S3 can be reduced by 8-15%, and carbon emissions per ton of iron can be reduced by 2-4%.

[0060] In particular, the blast furnace low-carbon smelting method based on slag system reconstruction can be used for effective volumes greater than 1000m³. From the adjustment of start-up parameters to the new slag system reaching stable performance, a transition period of about 5-7 days, or 120-168 hours, is required.

[0061] In particular, the blast furnace low-carbon smelting method based on slag system reconstruction can be used in modern ironmaking blast furnaces with an effective volume of 2000 m³ or more.

[0062] Example 1

[0063] This embodiment presents a low-carbon smelting method for blast furnaces based on slag system reconstruction, using a 3000m³ blast furnace as an example. 3 Taking a blast furnace as an example, the blast furnace low-carbon smelting method based on slag system reconstruction includes the following steps:

[0064] S1. Slag System Basic Parameter Design Stage: Under the original operating conditions, the final slag viscosity at 1500℃ is 0.48 Pa·s, basicity R=1.10, and MgO=7%. The final slag viscosity needs to be optimized. Based on the optimized final slag viscosity of 0.32 Pa·s at 1500℃, the composition of the final slag is selected to construct a slag system with "low viscosity final slag" corresponding to the final slag viscosity and composition. The construction method of the "low viscosity final slag" slag system is based on the actual operation of the blast furnace. Different combinations of binary basicity R=CaO / SiO2, Al2O3 mass fraction, and MgO content are selected. A slag viscosity database is measured and constructed. Slag combinations with a viscosity not exceeding 0.35 Pa·s at 1500℃ are selected as the target final slag composition to construct the "low viscosity final slag" slag system.

[0065] Through slag system reconstruction, the final slag target was adjusted to R=1.30, MgO=9%, Al2O3=14%, CaO=43.52%, and SiO2=33.48%.

[0066] Then, based on the slag system of "low viscosity final slag", the composition of the initial slag was back-inferred and its performance was evaluated;

[0067] Specifically, based on the final slag setting, and combined with the ash composition of coke and pulverized coal, the furnace charge structure and operating parameters, including coke ratio, coal ratio, and slag-iron ratio, the content of major oxides in the initial slag, including the content of CaO, SiO2, MgO, and Al2O3, is deduced. The FeO content needs to be set to 25%, and a model for deducing the initial slag is established based on material balance.

[0068] Fuel consumption per ton of iron: coke ratio 310 kg / tHM, coal ratio 200 kg / tHM; final slag amount: 350 kg / tHM. The composition of coke and pulverized coal is shown in Table 1 below.

[0069] Table 1

[0070]

[0071] The initial slag composition was estimated as follows: CaO = 37.76%, SiO2 = 22.08%, Al2O3 = 7.39%, MgO = 7.76%, FeO = 25%.

[0072] S2. Thermodynamic Matching Stage: Based on the initial slag composition, temperature field coordination is performed - the melting point and heat storage capacity of the initial slag are calculated, and the melting point of the initial slag is found to be 1430℃. At the same time, the heat storage capacity of the slag required per unit iron production is assessed to be 62940kJ. The required heat storage capacity of the slag meets the requirement of ensuring the stability of the temperature field in the blast furnace softening zone. Then, the heat compensation stage is carried out - high oxygen enrichment blast. The oxygen enrichment rate of the high oxygen enrichment blast is increased to 26% to meet the requirements of increasing the theoretical combustion temperature of the tuyeres to 2350℃ and meeting the requirements of high temperature heat intensity. The high temperature heat intensity requirement is to reach the minimum temperature at which the high melting point slag system can melt and have a suitable superheat. The furnace temperature - the minimum temperature at which the slag melts = 70±10℃.

[0073] S3. Construction of dynamic control system: Based on the analysis of the final slag composition and the results of viscosity measurement, it is necessary to dynamically correct the design of the basic parameters of the slag system and the thermodynamic matching stage, so as to finally realize the closed-loop control of slag performance.

[0074] In this embodiment, the fuel ratio that ultimately achieves closed-loop control of slag performance can be reduced by 8.5%, and carbon emissions per ton of iron can be reduced by 2.3%.

[0075] The blast furnace low-carbon smelting method based on slag system reconstruction in this embodiment typically has a transition period of about 5 days from the adjustment of start-up parameters to the new slag system reaching stable performance.

[0076] Example 2

[0077] This embodiment presents a low-carbon smelting method for blast furnaces based on slag system reconstruction, taking a 2800m³ blast furnace as an example, with the goal of improving smelting intensity. The method includes the following steps:

[0078] S1. Slag System Basic Parameter Design Stage: Under the original operating conditions, the final slag viscosity at 1500℃ was 0.46 Pa·s, basicity R=1.12, and MgO=7.2%. Through slag system reconstruction, the final slag target was adjusted to R=1.28, MgO=8.8%, Al2O3=15.5%, CaO=42.68%, and SiO2=33.34%, reducing the viscosity at 1500℃ to 0.33 Pa·s.

[0079] Fuel consumption per ton of iron: coke ratio 305 kg / tHM, coal ratio 195 kg / tHM; final slag quantity: 345 kg / tHM. Based on material balance back-calculation, FeO is set at 25%; the initial slag composition is obtained as follows: CaO=36.91%, SiO2=21.86%, Al2O3=8.11%, MgO=7.82%, FeO=25%.

[0080] S2, Thermodynamic Matching Stage: The initial slag melting point was calculated to be 1425℃, and the slag heat storage per unit iron production was 82000kJ / tHM; In order to match the increased smelting intensity, the oxygen enrichment rate was increased to 25.5%, the theoretical combustion temperature reached 2370℃, and the slag superheat was stabilized at 75℃.

[0081] S3. Construction of dynamic control system: Implement closed-loop control, and start correction when the viscosity of the final slag detected online is >0.35 Pa·s.

[0082] In this embodiment, the fuel ratio that ultimately achieves closed-loop control of slag performance is reduced from the original 465 kg / tHM to 427 kg / tHM, a decrease of approximately 8.2%; carbon emissions per ton of iron are reduced by approximately 35 kg / tHM (based on a baseline of 1.5 tCO2 / tHM, a decrease of approximately 2.3%). The overall adjustment cycle is approximately 120 hours.

[0083] Example 3

[0084] This embodiment presents a low-carbon smelting method for blast furnaces based on slag system reconstruction. Taking a 2500 m³ blast furnace as an example, this blast furnace uses high-alumina iron ore, resulting in a high Al2O3 content in the final slag. The method includes the following steps:

[0085] S1. Slag System Basic Parameter Design Stage: Under the original working conditions, the final slag viscosity at 1500℃ was 0.52 Pa·s, basicity R=1.15, MgO=8%, and Al2O3=17.5%. Through slag system reconstruction, the final slag target was adjusted to R=1.32, MgO=10.5%, Al2O3=17.0%, CaO=44.50%, and SiO2=33.71%, reducing the viscosity at 1500℃ to 0.34 Pa·s.

[0086] Fuel consumption per ton of iron: coke ratio 315 kg / tHM, coal ratio 185 kg / tHM; final slag quantity: 360 kg / tHM; based on material balance back-calculation, with FeO set at 25%, the initial slag composition is: CaO=35.82%, SiO2=22.14%, Al2O3=10.05%, MgO=9.79%, FeO=25%;

[0087] S2, Thermodynamic Matching Stage: The initial slag melting point was calculated to be 1450℃, and the slag heat storage per unit iron production was 86000kJ / tHM; In order to overcome the high melting point caused by high Al2O3, the oxygen enrichment rate was increased to 26.8%, the theoretical combustion temperature reached 2400℃, and the slag superheat was maintained at 65℃.

[0088] S3. Construction of dynamic control system: Implement closed-loop control, and start correction when the viscosity of the final slag detected online is >0.35 Pa·s or the Al2O3 content deviation is >5%.

[0089] In this embodiment, the fuel ratio that ultimately achieves closed-loop control of slag performance is reduced from the original 485 kg / tHM to 442 kg / tHM, a decrease of approximately 8.9%; carbon emissions per ton of iron are reduced by approximately 40 kg / tHM (a decrease of approximately 2.6%). The overall adjustment cycle is approximately 144 hours.

[0090] Example 4

[0091] This embodiment presents a low-carbon smelting method for blast furnaces based on slag system reconstruction. Taking a 3200m³ blast furnace as an example, this blast furnace has a low slag grade (TFe≈56%) and a large slag volume. The method includes the following steps:

[0092] S1. Slag System Basic Parameter Design Stage: Under the original working conditions, the final slag viscosity at 1500℃ was 0.50 Pa·s, basicity R=1.09, MgO=6.8%, and the slag-to-iron ratio reached 390 kg / tHM; through slag system reconstruction, the final slag target was adjusted to R=1.26, MgO=9.2%, Al2O3=13.8%, CaO=42.15%, SiO2=33.45%, reducing the viscosity at 1500℃ to 0.31 Pa·s;

[0093] Fuel consumption per ton of iron: coke ratio of 330 kg / tHM, coal ratio of 190 kg / tHM; based on material balance back-calculation, with FeO set at 25%, the initial slag composition is obtained as follows: CaO=34.28%, SiO2=23.91%, Al2O3=8.56%, MgO=8.35%, FeO=25%;

[0094] S2, Thermodynamic Matching Stage: The initial slag melting point was calculated to be 1418℃, and the slag heat storage per unit iron production was as high as 91000kJ / tHM; In order to provide sufficient heat to melt a large amount of slag, the oxygen enrichment rate was increased to 26.2%, the theoretical combustion temperature reached 2390℃, and the slag superheat was controlled at 80℃.

[0095] S3. Construction of dynamic control system: Implement closed-loop control, and start correction when the viscosity of the final slag detected online is >0.35 Pa·s or the alkalinity deviation is >0.05.

[0096] In this embodiment, the fuel ratio that ultimately achieves closed-loop control of slag performance is reduced from the original 505 kg / tHM to 460 kg / tHM, a decrease of approximately 8.9%; carbon emissions per ton of iron are reduced by approximately 42 kg / tHM (a decrease of approximately 2.8%). The overall adjustment cycle is approximately 168 hours.

[0097] Example 5

[0098] This embodiment presents a low-carbon smelting method for blast furnaces based on slag system reconstruction, taking a 4000m³ ultra-large blast furnace as an example. The method includes the following steps:

[0099] S1. Slag System Basic Parameter Design Stage: Under the original working conditions, the final slag viscosity at 1500℃ was 0.44 Pa·s, basicity R=1.18, and MgO=7.5%; through slag system reconstruction, the final slag target was adjusted to R=1.31, MgO=9.0%, Al2O3=15.2%, CaO=43.88%, and SiO2=33.50%, reducing the viscosity at 1500℃ to 0.30 Pa·s;

[0100] Fuel consumption per ton of iron: coke ratio 295 kg / tHM, coal ratio 205 kg / tHM, final slag amount: 340 kg / tHM; Based on material balance back-calculation, with FeO set at 25%, the initial slag composition is obtained as follows: CaO=38.92%, SiO2=22.87%, Al2O3=6.88%, MgO=8.33%, FeO=25%;

[0101] S2, Thermodynamic Matching Stage: The initial slag melting point was calculated to be 1438℃, and the slag heat storage per unit iron production was 83500kJ / tHM; In order to stably support high-intensity smelting in large furnace capacity, the oxygen enrichment rate was increased to 27.5%, the theoretical combustion temperature reached 2430℃, and the slag superheat was stabilized at 70℃.

[0102] S3. Construction of dynamic control system: Implement closed-loop control, and start correction when the viscosity of the final slag detected online is >0.35 Pa·s.

[0103] In this embodiment, the fuel ratio that ultimately achieves closed-loop control of slag performance is reduced from the original 455 kg / tHM to 416 kg / tHM, a decrease of approximately 8.6%; carbon emissions per ton of iron are reduced by approximately 37 kg / tHM (a decrease of approximately 2.4%). The overall adjustment cycle is approximately 120 hours.

[0104] Example 6

[0105] This embodiment demonstrates the rapid response and correction capabilities of the method under fluctuating furnace conditions. A 2000m³ blast furnace is used as an example.

[0106] S1. Slag System Basic Parameter Design Stage: Under the original stable operating conditions, the final slag viscosity was 0.33 Pa·s (R=1.27, MgO=8.5%). Online monitoring revealed that the final slag Al2O3 content suddenly increased from 14.5% to 16.0%, and the real-time viscosity rose to 0.39 Pa·s (exceeding the standard by 11%), triggering dynamic correction. The system calculation showed that MgO needed to be temporarily increased to 9.5% to optimize the viscosity.

[0107] S2, Thermodynamic Matching Stage: The system synchronously fine-tunes the oxygen enrichment rate to 25.8% to maintain the thermal regime, and the slag superheat is kept within the target range (70±10℃);

[0108] S3. Dynamic control system construction: The system automatically adjusts the furnace charge ratio. Within 36 hours, the final slag composition stabilizes (Al2O3=15.5%, MgO=9.3%), and the viscosity drops back to 0.34 Pa·s; during the transition period, the furnace operation is smooth, and the fuel ratio only fluctuates briefly before recovering.

[0109] This embodiment demonstrates that the closed-loop system can effectively cope with fluctuations and maintain stable performance within 24-48 hours.

[0110] In this embodiment, the fuel ratio that ultimately achieves closed-loop control of slag performance is reduced from 480 kg / tHM to 440 kg / tHM, a decrease of approximately 8.3%; carbon emissions per ton of iron are reduced by approximately 36 kg / tHM (a decrease of approximately 2.4%).

[0111] The above-mentioned solution, proposed by this invention, is a low-carbon smelting method for blast furnaces based on slag system reconstruction, which can solve the technical problems existing in the prior art, including: 1) the contradiction of traditional slag systems sacrificing fluidity to ensure alkali removal capacity; 2) the problem of excessively high viscosity of blast furnace final slag leading to deterioration of liquid permeability and air permeability; 3) the problem of low melting point of initial slag, insufficient heat storage capacity of the softening zone, and unstable temperature field; 4) the problem that existing technologies have single adjustment parameters or poor coordination, making it difficult to systematically optimize slag-iron flow and thermal efficiency, resulting in limited carbon reduction potential.

[0112] This invention designs basic slag parameters and selects different combinations of binary basicity (R=CaO / SiO2), Al2O3 mass fraction, and MgO content based on the actual operation of the blast furnace. It then measures and constructs a slag viscosity database and screens out slag combinations with a viscosity ≤0.35 Pa·s at 1500℃ as the target final slag composition.

[0113] This invention constructs a slag system with "low viscosity final slag," and by controlling the binary basicity and magnesium oxide content while reducing the final slag viscosity, it obtains a primary slag composition content that can improve the heat reserve of the furnace belly. Furthermore, based on a material balance-based model for inferring the primary slag composition, the obtained primary slag composition content has a small deviation, reducing the number of dynamic adjustments required. Specifically, it includes the following superior effects:

[0114] 1) Coordination between upper and lower parts, and consideration of functions: Starting with "low viscosity final slag", the primary slag with "high melting point and high heat storage" characteristics was designed in reverse through the synergistic regulation of alkalinity and MgO. For the first time, the contradiction between the fluidity of the lower part of the blast furnace and the thermal stability of the middle part was solved in the same slag system.

[0115] 2) Storing heat and ensuring stable operation: The high heat storage slag obtained forms an effective heat buffer zone in the softening zone, which enhances the stability of the thermal regime in the upper part of the blast furnace, improves the overall resistance to fluctuations of the blast furnace, and provides a reliable guarantee for the implementation of low-carbon and high-intensity smelting.

[0116] This invention, through temperature field coordination—calculation of initial slag melting point and heat storage capacity—enables the simultaneous calculation of the initial slag melting point using a multi-dimensional slag thermophysical property database and the assessment of the slag heat storage required per unit of iron production, thereby ensuring the stability of the temperature field in the blast furnace softening zone. Specifically, it offers the following superior effects:

[0117] 1) Quantitative design: The abstract concept of thermal stability of the soft melting zone is transformed into two core thermal parameters that can be accurately calculated and set: "initial slag melting point" and "heat storage per ton of iron".

[0118] 2) Synergistic buffering: The high melting point ensures the mechanical stability of the softening zone structure, while the high heat storage capacity provides a strong temperature buffering capability. The two work together to effectively suppress thermal fluctuations in the middle of the blast furnace.

[0119] 3) Support enhancement: This step ensures the smooth operation of the blast furnace from a thermal perspective, and provides the necessary thermal stability conditions for the safe implementation of enhanced smelting and carbon reduction measures such as "high oxygen enrichment, high alkalinity, and low viscosity".

[0120] This invention employs a thermal compensation stage—high-oxygen-enriched blast—to further increase the theoretical combustion temperature at the tuyeres by controlling the oxygen enrichment rate, thereby meeting the high-temperature thermal intensity requirements. The high-temperature thermal intensity requirement is to reach the minimum temperature at which the high-melting-point slag system can melt, with a slag superheat of 70±10℃.

[0121] This invention can dynamically correct the slag system settings and furnace charge matching based on online final slag composition analysis and viscosity measurement results, making the obtained results accurate and efficient, and easy to apply in industry; at the same time, it can realize closed-loop control of slag performance to reduce preparation costs, improve preparation efficiency, control carbon emissions, and be environmentally friendly.

[0122] In summary, compared with traditional blast furnace ironmaking, the method of this invention reconstructs the slag system through the optimization design of the final slag viscosity in the design of the basic parameters of the slag system, the back-inference and performance evaluation of the slag composition, the coordination of the temperature field with thermodynamic matching, the calculation of the initial slag melting point and heat storage capacity and the heat compensation stage, the high oxygen enrichment blast, and the construction of a dynamic control system. This method is simple and easy to operate, with multi-parameter coordinated control. The technical approach overcomes the technical prejudice that "the basicity of traditional blast furnace smelting cannot be too high, which will reduce the viscosity of the molten slag and lead to many technical problems, including slag and iron sticking and blockage, and unstable temperature field in the blast furnace softening zone." The slag system reconstruction has high accuracy, is environmentally friendly, low cost and high efficiency, and is conducive to large-scale industrial production and application.

[0123] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0124] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0125] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0126] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A blast furnace low-carbon smelting method based on slag system reconstruction, characterized in that, The blast furnace low-carbon smelting method based on slag system reconstruction includes the following steps: S1. Slag System Basic Parameter Design Stage: It is necessary to optimize the final slag viscosity and select the final slag components based on the optimized final slag viscosity to construct a slag system with "low viscosity final slag" corresponding to the final slag viscosity and final slag components; then, the initial slag components are back-inferred and the performance is evaluated based on the slag system with "low viscosity final slag". S2. Thermodynamic matching stage: Temperature field coordination is carried out based on the initial slag composition - the melting point and heat storage capacity of the initial slag are calculated to obtain the melting point of the initial slag. At the same time, the heat storage capacity of the slag required per unit iron production is evaluated. The required heat storage capacity of the slag meets the requirements to ensure the stability of the temperature field in the blast furnace softening zone. Then, the heat compensation stage is carried out - high oxygen enrichment blast. The oxygen enrichment rate of the high oxygen enrichment blast needs to meet the requirement of increasing the theoretical combustion temperature of the tuyeres to meet the high temperature heat intensity. S3. Construction of dynamic control system: Based on the analysis of the final slag composition and the results of viscosity measurement, the design of the basic parameters of the slag system and the thermodynamic matching stage are dynamically corrected to ultimately achieve closed-loop control of slag performance.

2. The blast furnace low-carbon smelting method based on slag system reconstruction according to claim 1, characterized in that, The viscosity of the final slag after optimization design in S1 is no higher than 0.35 Pa·s at 1500℃, and the binary basicity R of the "low viscosity final slag" is no lower than 1.

25.

3. The blast furnace low-carbon smelting method based on slag system reconstruction according to claim 2, characterized in that, In S1, the viscosity of the final slag is reduced synergistically by increasing the binary basicity R=CaO / SiO2 and increasing the MgO content.

4. The blast furnace low-carbon smelting method based on slag system reconstruction according to claim 2, characterized in that, The slag system construction method of "low viscosity final slag" in S1 is based on the actual operation of the blast furnace. Different combinations of binary basicity R=CaO / SiO2, Al2O3 mass fraction, and MgO content are selected. The slag viscosity database is measured and constructed. Slag combinations with viscosity not higher than 0.35 Pa·s at 1500℃ are selected as target final slag components to construct the slag system of "low viscosity final slag".

5. The blast furnace low-carbon smelting method based on slag system reconstruction according to claim 1, characterized in that, Based on the final slag setting in S1, and combined with the ash composition of coke and pulverized coal, the furnace charge structure, and operating parameters, including coke ratio, coal ratio, and slag-iron ratio, the content of major oxides in the initial slag, including the content of CaO, SiO2, MgO, and Al2O3, is deduced. The FeO content needs to be set to 25%, and a model for deducing the initial slag is established based on material balance.

6. The blast furnace low-carbon smelting method based on slag system reconstruction according to claim 1, characterized in that, The melting point of the primary slag in S2 is not lower than 1400℃, and the slag heat storage required per unit ton of iron production is not lower than 62940kJ.

7. The blast furnace low-carbon smelting method based on slag system reconstruction according to claim 1, characterized in that, The oxygen enrichment rate of the high oxygen-enriched blast in S2 needs to be set to no less than 24%, the theoretical combustion temperature of the tuyeres needs to be increased to no less than 2350℃, and the high temperature heat intensity requirement is to reach the minimum temperature at which the high melting point slag system can melt and the slag superheat is 70±10℃.

8. The blast furnace low-carbon smelting method based on slag system reconstruction according to claim 1, characterized in that, In S3, the fuel ratio that ultimately achieves closed-loop control of slag performance can be reduced by 8-15%, and carbon emissions per ton of iron can be reduced by 2-4%.

9. The blast furnace low-carbon smelting method based on slag system reconstruction according to claim 1, characterized in that, The blast furnace low-carbon smelting method based on slag system reconstruction can be used for effective volumes greater than 1000m³. From the adjustment of start-up parameters to the new slag system reaching stable performance, a transition period of 5-7 days, or 120-168 hours, is required.

10. The blast furnace low-carbon smelting method based on slag system reconstruction according to claim 1, characterized in that, The blast furnace low-carbon smelting method based on slag system reconstruction can be used in modern ironmaking blast furnaces with an effective volume of 2000m³ or more.

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