Blast Furnace Process Research Articles

The development of the blast furnace metallurgy of the iron in Slovakia

Easily available sources of iron ore, the abundance of hydropower, and wood for charcoal were the prerequisites for the development of iron metallurgy in Slovakia. Since the 16th century, the bloomery process used in iron metallurgy has been gradually replaced by the blast furnace process. This new process was more economical, but it required extremely high investments. The steam engine replaced the unreliable water power in the blowing process, and coke replaced charcoal. Especially due to economic problems, the first blast furnaces in Slovakia started to be built about two hundred years later than in Western Europe. Despite the promising start, the installation of steam engines was lagging. A major drawback was the lack of road and rail networks combined with the absence of local coking coal. The introductory part of the paper compares chronologically the individual stages of the development of blast furnace production in Slovakia and abroad. Next, the paper presents comprehensive results of the analysis of samples of the slag found at 59 sites of extinct ironworks with a blast furnace, localised until now. The samples were analysed by metallographic, chemical, spectral (secondary and trace elements), and X-ray methods. In the past, these data were published with territorial restrictions and mostly in a language other than Slovak. The contents of secondary and trace elements in slag from individual sites using cluster analysis and also metallic iron content in slags categorised according to owners of the blast furnaces and the slag basicity are compared.

Thermal reactivity and flowability of pulverized coal blending with iron-bearing dust injection in blast furnace process

Pulverized coal (PC) blending with iron-bearing dust (IBD) injection technology in blast furnace (BF) iron-making process was proposed to valorize the IBD. Three aspects containing the co-flow property of PC and IBD, thermal reactivity and corresponding kinetics during the PC combustion process, as well as thermal variation and unburned PC distribution in BF were the main focuses of the present work. It has found that the Carr-flowability indexes of PC and IBD appear little difference. Their blends can be smoothly transported when adding portion of the IBD is less than 6%. In addition, comprehensive combustibility index (S), ignition index (Ci), and burnout index (Db) of the PC are improved when the mass fraction of the IBD enhances from 0% to 3%, and 6%, which proves that blending with the IBD can accelerate the PC combustion process. Moreover, the combustion activation energy (E) decreases after adding the IBD, which supports the improved thermal reactivity. Also, the accumulation of unburned PC in BF presents a decline tendency, which may promote the permeability of BF and help enhancing the pulverized coal injection dosage.

THE ESTIMATION OF THE EFFECT OF COKE, OBTAINED WITH PARTICIPATION OF VOLUME-MODIFYING ADDITIVES, ON THE TECHNICAL AND ECONOMIC INDICATORS OF BLUST FURNACE SMELTING

The article deals with the effect of the coke resistance index CSR (Coke Strength after Reaction) on the technical and economic indicators of the blast furnace process. It is shown that in the production of metallurgical coke using volume-modifying additives in the amount of 0.25% by weight of the coal load, its strength improves, in particular, index CSR. As a volume-modifying additives, α-Al2O3 electrocorundum and α-SiC carborundum with a particle size of <45 μm and vibromilenum α-SiC carborundum with a particle size <12 μm were used.
 Due to the introduction of fine powders of electrocorundum and carborundum into the coal charge, the maximum increase in the coke post-reaction strength index (CSR) by 7.6% was obtained.
 The influence of changes in individual indicators of coke quality on its consumption and productivity of the blast furnace was assessed in accordance with the guidance document of the metallurgical division of Metinvest Holding LLC. This document contains a detailed methodology for use in analyzing fluctuations in specific coke consumption and throughput of blast furnaces influenced by changes in blast furnace process parameters (by factor analysis). This technique is based on quantitative relationships between changing parameters (factors) and specific coke consumption (blast furnace productivity).
 There has been made an expert technical and economic assessment of the feasibility of introducing 0.25% fine powdered α-Al2O3 and α-SiC powders into the mixture from the point of view of blast-furnace production with pulverized fuel injection technology. The results show that, despite the increase in the cost of coke with the introduction of volume-modifying additives into the mixture, a reduction in the cost of iron can be achieved due to the expected reduction in the specific consumption of coke due to an increase in its post-reaction strength.

Simulation of the Effects of Hydrogen Injection on the Main Indicators of Blast Furnace and Carbon Dioxide Emission Reduction by Zero-Dimensional Model

The steel industry accounts for about 7% of the total human carbon dioxide emissions, and faces enormous pressure to reduce emissions, especially the blast furnace (BF) process with high carbon dioxide emissions. BF hydrogen injection is one of the important technical measures for emission reduction. However, there are still few studies on the limit of hydrogen injection in BF and the influences of hydrogen injection on the changes of main indicators of BF. To evaluate the limits of BF hydrogen injection and these effects, this paper introduces in detail the application of Excel MMULT (MINVERSE (zone 1), (zone 2)) function to build BF mass and heat balance model and application of the Generalized Reduced Gradient (GRG) nonlinear optimizer of Excel Solver Add-In for BF operation optimization. The paper simulates the effects of hydrogen injection on the replacement of BF coke and pulverized coal, the reduction of CO₂ emission, the increase of production, and the changes of raceway adiabatic flame temperature (RAFT) and top gas temperature (TGT), the use of blast temperature (BT), and oxygen enrichment for thermal compensation. The possible limits of hydrogen injection are simulated. The influences on BF direct reduction degree (Dr), CO and H₂ utilization rate (ηCO and ηH₂) are also simulated. Further, the influences of hydrogen preheating injection on coke ratio, CO₂ emission reduction and use of BT, oxygen-enrichment for thermal compensation are simulated. The paper comprehensively and quantitatively evaluated the various aspects of BF hydrogen injection. The simulation results show that when hydrogen is injected at room temperature (298 K), under condition of full coke, 1250°C BT, oxygen enrichment and maintaining 1800°C RAFT, the maximum CO₂ emission reduction of the BF can reach ~30%. If the allowable RAFT is 1900°C, the maximum hydrogen injection volume is about 1/3 less than 1800°C, and the maximum CO₂ emission reduction will be ~20%. 1 kg/thm of hydrogen injected can replace about 2 kg/thm of carbon; this value varies with BT and oxygen enrichment rate, but is not affected by the composition of the mixed ore.

The CO2 reduction potential for the oxygen blast furnace with CO2 capture and storage under hydrogen-enriched conditions

The CO2 emission reduction of blast furnace (BF) is critical to the clean and sustainable development of the steel industry. Herein, we studied the CO2 emission reduction potential of oxygen blast furnace (OBF) and oxygen blast furnace under hydrogen-enriched conditions (OBFh-ec) with CO2 capture and storage, via establishing mathematical models, including the stack and bosh model, the combustion zone model, and the gas recycling system model. The in-furnace status, mass and energy consumption, and the CO2 emission of the OBF under four typical conditions were analyzed based on the models. Considering the relationship between BF and upstream and downstream processes, the CO2 emission that BF processes should bear in an integrated steel mill was calculated. The results indicated that, compared with the conventional BF, the CO2 emissions of OBFh-ec decreased by 9-14%, and decreased by 38-44% when the CO2 storage technology was used. Importantly, the hydrogen-enriched injection will affect the carbon emission reduction effect of CO2 capture and storage. The fuel consumption and the comprehensive energy consumption of OBFh-ec decreased. The mechanism in the CO2 emission reduction of OBFh-ec was interpreted based on analyzing the chemical reactions, temperature, and mass flow in the furnace. This study has important implications for understanding the CO2 reduction potential of the OBF using CO2 capture and storage with hydrogenous fuel injections.

Numerical Study of Gas Flow and Temperature Patterns in the Blast Furnace Throat

The gas distribution in the shaft is of key importance for the performance of the blast furnace process, since it affects the way in which the burden is heated and reduced, and also the pressure drop in the shaft and cohesive zone. Traditionally, the gas distribution is followed by gas temperature measurements at several points over the radius or diagonal by the above-burden probes, but novel acoustic techniques can estimate the gas temperature over the full cross section of the throat. A fundamental problem is that the gas is redistributed in the upper bed and above it, so the measured profile may no longer reflect the conditions in the shaft. This paper studies the gas redistribution by a CFD model of the throat region, neglecting heat transfer to the bed and walls. It is demonstrated that strong redistribution and downward-swirling flows may occur, which affect the measurements. The arising conditions under different assumptions of the bed state are studied, and the dynamics of the changes are also briefly analyzed. A comparison of the findings of the computational model with acoustic measurements of the gas temperatures in the throat of two industrial blast furnaces reveals a good resemblance. The results of the study sheds light on the complex flow conditions of the gas in the blast furnace throat region and can be used to interpret information from measuring devices and to study how their positioning affects the measurements.

Attention mechanism-aided data- and knowledge-driven soft sensors for predicting blast furnace gas generation

Blast furnace gas (BFG) is an important energy-carrying byproduct of the iron and steel industry. High-accuracy prediction of BFG generation is the basis of the dynamic balance of gas supply–demand and energy scheduling. However, due to instrument faults, measurements of BFG are discontinuous or inaccurate, making it difficult to accurately predict future BFG generation by using historical data, which seriously restricts the development of intelligent management and coordination between various gas sources and users. To solve this problem, an attention mechanism-aided data- and knowledge-driven soft sensor is proposed to predict BFG generation. To reduce the complexity of the samples, the proposed method selects key features to simplify the model input by using attention mechanism. Genetic algorithm (GA) is used to optimize hyperparameters to improve the stability of the model. In addition, combined with the knowledge of the blast furnace process, the prediction results are reasonably constrained. The results show that the prediction accuracy of the A-DK-GA-XGBoost model is higher than that of the other prediction models, with a mean absolute error of 68.2 m3/min, a symmetric mean absolute percentage error of 0.83%, a root mean square error of 68.71 m3/min, and an R squared of 99.06%. It is proven that the A-DK-GA-XGBoost model has superior performance.

Individual and combined effect of operating and geometric parameters on combustion behaviour of low and high volatile coals

ABSTRACT Pulverized coal injection technology plays a crucial role in controlling the blast furnace process but increasing the combustion efficiency of coal remains a challenge. Towards this, the manuscript attempts to examine the performance of different coals subjected to different operating and geometric parameters through a validated numerical model. Two coals with different volatile matter have been selected for this study while oxygen enrichment, lance position, and particle size distribution have been varied. Among all parameters, particle fineness has proven to be the major contributor towards improving burnout. The underlying mechanism has been explained in terms of oxygen distribution and particle temperature. In addition, the combined effect of all parameters increases the final conversion by 6% and 10% for high and low volatile coals respectively. Ease of volatile release plays an important role in controlling the overall burnout where a higher release rate for high volatile coal somewhat compensates for the impact of the parameters studied.

A Data-Based Compact High-Order Volterra Model for Complex Blast Furnace System

In this article, a data-based compact Volterra model is constructed to carry out the silicon prediction task. The main motivations are to, on the one hand, make better use of the strong memory ability of the Volterra series, which is suitable for reflecting the large inertia of the blast furnace process, on the other hand, overcome the difficulty that high complexity of the original Volterra models may result in serious overfitting. Six kinds of models, including single-input and two-input linear, second-order and third-order compact Volterra models, are successively designed and verified through a real blast furnace case. The reasonable agreement between the predicted values and the observed values indicates the compact Volterra model, especially the single-input third-order Volterra model, are powerful and competitive for describing the complex blast furnace system. The experimental results can serve as a guide for the blast furnace operators to judge the in-furnace thermal state change in time and further provide an indication on how to control the blast furnace in advance.

A novel knowledge enhanced graph neural networks for fault diagnosis with application to blast furnace process safety

With the advent of industry 4.0, many traditional industries are moving toward automation, intelligence, and large-scale. The continuous expansion of production scale also means that the structure of industrial processes and the interactions between subsystems are becoming increas- ingly complex, which also introduced potential safety risks into the actual production. Due to the complexity and danger of the production process, the process safety of the modern blast furnace (BF) ironmaking process is a prominent problem. In this paper, a novel fault detection and di- agnosis (FDD) framework is proposed, which can detect the abnormality and infer the root cause with no need of building an accurate mechanism model as the traditional methods. After a fault is detected, to better learn fault propagation mechanisms of the BF ironmaking process, a process knowledge model was proposed and integrated with the data-driven approaches for fault diagnosis. Then, to discover the causalities matrix of the faulty data generating procedure, a novel root cause analysis method based on Graph Neural Networks (GNN) was developed. Moreover, to accurately describe the causal interactions of faulty variables and solve the problem of the redundant edges in the causal discovery, the process knowledge constraint item was added to the GNN model to guarantee the discovered causal graph matches with the practical domain knowledge to strengthen its application in the practical industry. The experimental results on real BF data set and a bench- mark data set (The RT 580 data set) demonstrate that our algorithm not only obtains a significant improvement over other methods but also has a favorable application in the industrial process.

Technological roadmap towards optimal decarbonization development of China's iron and steel industry

China's iron and steel (IS) industry contributes approximately 16 % of the nation's total CO2 emissions. This study evaluates the environmental impact of each step in the production process based on the life cycle assessment method. It then explores potential deep decarbonisation pathways, developing an integrated dynamic model to meet the carbon neutrality target. The results reveal three primary findings. (1) In 2020, the blast furnace-basic oxygen furnace contributed significantly to the global warming potential −1.77 E−8 kg CO2 equivalents per year (eq/yr) higher than the electric arc furnace—and the blast furnace process makes the largest contribution in ironmaking (8.9E−9 kg CO2 eq/yr). (2) Converter negative energy steelmaking technology has the highest energy savings at 39.07 million tons of coal equivalent (Mtce) and an emissions-reduction potential of 72.01 Mt. Its mitigation cost is 69 CNY/t CO2, followed by thick-layer sintering (30.21 Mtce, 61.21 Mt. and 70 CNY/t CO2) and the application of dry vacuum system for molten steel degassing circulation (26.17 Mtce, 56.03 Mt. and 102 CNY/t CO2). (3) Technological improvement could significantly impact the IS industry, reducing CO2 emissions through production structure improvement, technological development and ultra-low emissions technology, from 789 Mt. in a business-as-usual scenario to 516 Mt., 261 Mt. and 157 Mt. in 2060, respectively.

Pyrolysis Behavior of Pyrite under a CO-H2 Atmosphere.

The transformation behavior of pyrite (FeS2) in the blast furnace process is critical to control the formation and emission of gaseous sulfides in the top gas of ironmaking but has seldom been explored. In present work, the pyrolysis of pyrite from 200 to 900 °C under a CO–H2 atmosphere was investigated by thermal-gravimetric and mass spectrometry. The thermodynamic theoretical calculations were carried out to further understand the transformation process. The results show that FeS2 is almost completely reduced to FeS under various CO–H2 atmospheres. H2S and carbonyl sulfide (COS) are the main gaseous sulfides formed through the pyrolysis reactions of FeS2 under a CO–H2 atmosphere. A higher H2 concentration can reduce the pyrolysis reaction temperature of FeS2, which is favorable for the conversion of sulfides to H2S, while a higher CO concentration promotes the conversion of sulfides to COS. Besides, the pyrolysis products of FeS2 by order from the former to latter under a strong reductive atmosphere (CO–H2) with increasing temperature are as follows: COS → S → H2S → S2 → CS2.

Material, energy and exergy flows of the oxygen blast furnace process with sintering flue gas injection

The SO2 and NOx are typical hazardous substances for atmospheric environment and their emission loads are strictly limited in the steelmaking or other relevant chemical engineering industries. To effectively treat the SO2 and NOx in the sintering flue gas, the oxygen blast furnace is considered as a novel SO2 and NOx purification equipment. In this study, a mathematical model is established to analyze the material, energy and exergy flows of this novel system. Three simulation cases including ordinary blast furnace without sintering flue gas injection (Case 0), medium oxygen-enriched blast furnace (Case 1) and full oxygen blast furnace (Case 2) are studied. The results show that the maximum amount of the injected sintering flue gas in Cases 1 and 2 is 2240 m3/tHM and 3027 m3/tHM, respectively. The energy efficiency of Cases 1 and 2 is 24.88% and 29.17% higher than that of Case 0, but the exergy efficiency reduces by 0.62%, 0.45%. In Case 2, the treatment quantities of SO2 and NO2 are 1498.37 g/tHM and 898.48 g/tHM, respectively. Therefore, this process is a promising route of promoting the cleaner production in the steelmaking or other relevant chemical engineering industries.

Numerical investigation of coke oven gas (COG) injection into an ironmaking blast furnace (BF)

Blast furnace (BF) ironmaking is the predominating process for producing hot metal (HM). It consumes huge quantities of carbonaceous fuel materials and leads to massive CO2 emissions. The injection of coke oven gas (COG) into the BF is considered a promising solution. It recovers the COG that is a kind of off-gas in the steelwork, and reuses the COG as an H2-intensive fuel in the BF to partially replace the use of carbonaceous fuel materials. However, thus far, the technology is not widely adopted, mainly due to the lack of understanding regarding the effects of key operational parameters of COG injection on BF performance. In addition, the coupling effect of COG injection and BF operation particularly the control at furnace top is not clear, leading to the low utilization efficiency. In this work, a continuum-based BF process model is developed and validated to consider the injection of COG into a commercial scale BF through the tuyere. The model is validated by comparing the calculated key performance indicators with those measured in production. The impact of COG injection rate is studied and its coupling effects with top burden distribution have also been clarified. The simulation results show that an increased COG injection rate leads to improved BF performance, in terms of increased productivity and decreased consumption of carbonaceous fuel materials. However, the utilization efficiency of COG and the replacement ratio of carbonaceous fuel materials by COG is decreased. An optimum top burden distribution can be identified, which can improve the utilization efficiency of injected COG and achieve a relatively high replacement ratio. The findings from this work should be useful to guide production of BF with H2-intensive fuel injection, which helps to save the use of carbonaceous fuel materials and reduce CO2 emission.

CHANGES IN STRENGTH AND REDUCIBILITY OF IRON ORE SINTERS WITH INCREASING BASICITY

Improving the quality characteristics of iron ore materials is one of the most effective ways to reduce fuel consumption in pig iron production, improving the technical and economic performance of the blast furnace process. The quality of finished products depends on a whole range of technological parameters, advancing along its chain, it is possible to identify the process of formation and nucleation of minerals, because it is the mineral composition of the ore grains bundle that determines and influences of many pyrometallurgical processes, being the main carrier of the strength of fluxed sinters. One of the most important criteria for qualitative evaluation of sinter is its cold strength. Based on the importance of this criterion, a comparative analysis of studies of the cold strength of iron-ore sinters of different chemical compositions has been performed. Understanding that the cold strength index is a tool to analyze the sintering process and mechanical treatment of sintered iron ore allowed us to determine the importance of one of the objectives of the study ‒ to show the change in the character of the strength curve of sintering from the basicity. An additional difficulty was that the initial charge of iron ore concentrates contained magnetite of homogeneous and heterogeneous structure. It is worth distinguishing the ability of magnetites of the two types to participate in the melt formation. Thus, the characteristic feature of homogeneous magnetite is that it takes a direct part in the evolution of bonds, and the growth of strength of sinters occurs as a result of the change of silicate bonds to ferritic ones. As a result of a separate study of magnetite of heterogeneous structure, it was possible to prove that its participation in melt formation is not limited, as previously thought, but excluded, which subsequently led to the hypothesis of predicting the existence of an interval of “failure” of cold strength of offset iron ore sinter, which in the future will allow to predict the quality of the finished product at any layout of charge materials. In addition to the index of cold strength, which determines the blast furnace operation, productivity and coke consumption, we also refer to reducing ability. The MISIS laboratory has carried out the testing on the basis of which the results of determining the reducibility of sinters from charge mixture are presented; the ore part consists of 100% concentrate containing heterogeneous magnetite for three basicity levels (1.4; 1.6 and 3.0 units).

Research on the Removal of Sodium from Vanadium Tailings by Calcification Roasting and NaOH Leaching

Vanadium tailings are a common solid waste in the vanadium industry. As they are rich in Fe, vanadium tailings could be a potential raw material for the blast furnace. However, the presence of approximately 4% Na2O in vanadium tailings is a major impediment to its return to the blast furnace. A novel method for removing sodium from vanadium tailings by calcification roasting and subsequent NaOH leaching was proposed in this work. The method demonstrated that calcification roasting of vanadium tailings can not only volatilize a part of sodium but also facilitate the dissolution of sodium during the subsequent NaOH leaching process. The thermodynamic analysis and behaviors of vanadium tailings during calcification roasting were systematically investigated. The transformation of sodium-containing phases in vanadium tailings during calcification roasting was studied. Further, the promoting effect of calcification roasting on sodium leaching by NaOH was clarified. The total removal efficiency of sodium was 80.37% under optimal conditions, and the residue obtained after sodium removal can be used as a raw material in the blast furnace process for in-plant recycling.

Comprehensive index of compound blast furnace smelting

An actual direction in the development of blast-furnace smelting technology is the implementation of stable operating modes of blast furnaces in terms of the parameters of the used charge materials and hot combined blast. For this purpose, complex indicators characterizing the thermal and reduction modes of blast furnace smelting, and integral indicators of iron ore raw materials (IORM) quality are being studied. The object of the study is the blast furnace process under the conditions of PJSC NLMK. The database of the main indicators of the operation of blast furnaces No. 4, 6 and 7 for the period 2013–2018 was analyzed. The furnaces operate under raw material conditions, with similar combined blast parameters and coke consumption. When the consumption of natural gas, pulverized coal and process oxygen changes, the values of the degree of compensation (the ratio of the consumption of reducing additives to the consumption of process oxygen) are in the range of 0.9–1.1. This provides a constant level of hearth heating, stability of the gas-dynamic mode of melting and coke consumption. At the same time, the different level of development of the processes of indirect (Ri) and direct (rd) reduction in blast furnaces No. 4, 6 and 7 makes it possible to perform correct studies of the features of blast furnace smelting in a wide range of Ri and rd values. It has been established that under the conditions of stable operation of blast furnaces on raw materials from sinter and pellets using combined blast, the type of dependence of the sulfur and silicon content in pig iron on the values of the integrated iron ore raw materials quality index is determined by degree development level of direct reduction processes rd. It has been established that the mode of blast furnace smelting with natural gas, pulverized coal and process oxygen, characterized by the level of rd values less than 20–25 %, is distinguished by the presence of a pronounced extreme dependence of coke consumption and productivity on the parameters of the combined blast.

Analysis of slag mode of blast furnace melting using model decision support systems

The article presents a balance model of the blast furnace process improved by the researchers from UrFU and PJSC “Magnitogorsk Iron and Steel Works” (MMK). It generally represents a system of deterministic dependencies characterizing the thermal, reduction, gas dynamic, blast and slag modes of blast furnace melting. The basic principle underlying the model is full-scale mathematical modeling. Indicators characterizing the properties of the final slag for implementation of normal slag mode of blast furnace melting (slag viscosity in the temperature range of 1350 – 1550 °C, as well as values of the slag viscosity gradients) were proposed. The slag viscosity gradient, along with the acceptable ranges of slag viscosity at different slag temperatures, are used in modeling the slag mode as limiting factors for the diagnosis of slag mode. Selection of the limit values of each of the ranges and the viscosity gradient is carried out by the method of expert evaluation. Structure of the model for calculating the parameters of the final slag is considered. Using a mathematical model of the blast furnace process, analysis of the slag mode of blast furnace melting was performed according to the actual indicators of their operation. It was established that desulfurizing ability of the slag is insufficiently used, as a result of which cast iron of reduced quality is smelted both in terms of content of sulfur and silicon. Change in characteristics of the slag mode, other things being equal, has a positive effect on gas permeability in the slag formation zone, reducing capacity of the gas and productivity of the blast furnace increase, as well as the consumption of coke decreases. The authors describe the results of design calculations of the MMK furnace performance indicators when changing the composition of loaded materials. Recommendations on the slag optimal basicity are given. Calculations showed that the optimal basicity of the final slag, which ensures its maximum liquid mobility, for operating conditions of blast furnaces of the combine is 1.04 – 1.05 for the CaO/SiO2 ratio and 1.30 – 1.32 for the (CaO + MgO)/SiO2 ratio.

Preparation and Consolidation Mechanism of Nickel Laterite Carbon Composite Hot Briquette

Blast furnace smelting process has advantages in producing ferronickel products because of its low comprehensive energy consumption and high production efficiency. However, laterite nickel ore has poor performance of pellets and lump ore due to its own characteristics. At present, the main lumping method is low basicity sinter, which is difficult to optimize the charge structure. This paper mainly studies the preparation process of laterite nickel carbon composite hot briquette (LN-CCHB) and the influence of process parameters on the basic compressive strength properties, so as to explore a new charge for smelting laterite nickel in blast furnace process. Results showed that the influence of pressure and temperature of hot briquette on the compressive strength of NL-CCHB is obvious. The compressive strength of NL-CCHB increases with the increase of briquetting pressure increases first and then decreases with the increase of hot briquetting temperature. The FC/O ratio (the ratio of the fixed carbon mol (C) in coal to the reducible oxygen mol (O) in iron oxides) has little effect on the compressive strength of NL-CCHB. In the experimental range, the mixture of laterite nickel ore and pulverized coal can obtain NL-CCHB with compressive strength of more than 1300N after hot briquetting. After heat treatment, NL-CCHB with compressive strength of more than 1800N can be obtained. The optimum hot briquetting process parameters are: FC/O ratio 1.25, hot briquetting temperature 450°C, hot briquetting pressure 80MPa. The optimum heat treatment process parameters are: FC/O ratio 1.50, heat treatment temperature 550°C.

Optimizing the Coinjection of Natural Gas and Pulverized Coal for Indian Blast Furnaces Toward Productivity Gains and Lower‐Carbon Emissions

India's stated goals to more than double steelmaking production capacity by 2030 merit consideration of new technical pathways for productivity gains and emission reduction. Already the second‐largest steel producer globally, India primarily relies on coal‐based technologies for ironmaking, with heavy reliance on imported metallurgical‐grade coal. This study develops an integrated thermodynamic modeling approach by iteratively coupling the raceway adiabatic flame temperature (RAFT) and Rist models to explore the ability to consider various hydrocarbon injectants through the tuyeres of a blast furnace. Based on the thermodynamic criteria set in the modeling framework, optimal coinjection rates for natural gas (as a low‐carbon feed) are identified along with pulverized coal injection as a function of various operating parameters, including top gas temperature, RAFT temperature, and ore processing (pelletization). The potential for productivity gains and CO2 emission reduction in the blast furnace process is discussed. While the study bears specificity to Indian operating conditions related to raw material composition and blast furnace process parameters, the learnings may be applicable to other studies in the global context, with potential extension to deeper decarbonization pathways, such as increased use of hydrogen.