Blast Furnace Shaft Research Articles

Novel experimental method to simulate reduction behaviour of burden in blast furnace shaft

In order to evaluate the effects of CO and H2 for the gas–solid reaction behaviour of the ferrous burden and coke in blast furnace shaft, a near-steady-state simulation test method of the blast furnace shaft was designed. The reduction behaviour of the ferrous burden, carbon solution loss reaction under different temperatures and atmospheres, and the effect of hydrogen enrichment on the CO gas utilisation ratio were investigated. The results show that above 830 °C, the reduction degrees of different ferrous burden structures under H2 atmosphere are higher than that under CO atmosphere. Better reduction degradation behaviour could be obtained under the hydrogen-rich atmosphere. The H2O generated under H2 atmosphere could promote the carbon solution loss reaction. The solution loss ratio reaching the maximum at 950 °C. Under hydrogen-rich atmosphere, CO gas utilisation ratio increased with the increased H2 concentration due to the effects of the products H2O and CO2.

Development and implementation of technological measures to extend the campaign of blast furnace No. 5 of PJSC Severstal

The work presents generalized experience in the development and implementation at PJSC Severstal of technological measures to extend the campaign of blast furnace No. 5. The authors carried out an analysis, identified and described the problem areas, generalized the principles for ensuring the safety of the shaft lining, boshes and metal receiver of the blast furnace. The results of a study of the working space of blast furnace No. 5 in 2006 are also presented. The identified technological factors ensure an increase in duration of the unit campaign. Technolo­gical measures are given for: washing the blast furnace hearth, reducing chemical erosion of the carbon blocks of the hearth and flange, forming a protective skull in the blast furnace shaft, special methods for loading solid coke substitutes, and organizing an effective structure of the charge column in the blast furnace. It is necessary to use digital models integrated into the blast furnace expert system for operational control of blast furnace technology. The results of the current blast furnace campaign were compared with previous ones. It was proven that the systematic use of all elements of the developed technology makes it possible to achieve high economic indicators while exceeding the standard duration of the campaign by 1.75 times. Experience in technology development made it possible to increase the furnace campaign duration to 17.46 years, achieve a reduction in specific coke consumption by 15.9 %, and increase the specific consumption of natural gas for cast iron smelting by 46.4 %; reduce the specific carbon consumption for cast iron smelting by 6.3 %.

Development of stabilization measures aimed at removing zinc with smelting products and accumulating titanium in the hearth of a blast furnace

AbstractThis paper presents the results of the development of stabilization measures aimed at the removal of zinc with the products of melting and accumulation of titanium in the hearth of a blast furnace. The relevance of the development and use in practice of such measures is due to the unstable fuel and raw materials conditions for the production of cast iron, when their stabilization is a complex and difficult task, as well as the need to extend the campaign of blast furnaces during the overhaul period. The negative effect of zinc oxides on the condition of the blast furnace shaft lining, accompanied by slab formation, and the overconsumption of specific coke consumption, which occurs when zinc circulates in the volume of the blast furnace, require measures to remove zinc from the smelting products. The article proposes such measures, which consist of flushing according to the proposed schedule during the operation of the blast furnace at planned blowing parameters and with the provision of the necessary thermal reserve. In order to lengthen the campaign of a blast furnace, one of the most common methods for protecting the hearth lining is the periodic introduction of titanium‐containing materials into the charge of blast furnaces. The entry of titanium oxides into the furnace, as a rule, is ensured by the use of concentrate or specially prepared ilmenite briquettes with a high titanium content as part of the sinter charge, which can be introduced directly into the composition of the blast furnace charge. The article analyzes the experience of using titanium‐containing materials as part of a blast furnace charge and formulates measures to intensify skull formation in the hearth.

Effects of different atmosphere on reaction behaviors of metallised burden

ABSTRACT The utilisation of metallised burden in blast furnace (BF) as a way of CO2 emission reduction has been widely considered. One of the major concerns is its reoxidation by CO2 in the upper part of BFs. In this study, the non-isothermal reaction behaviours of metallised burden with a metallisation ratio of 70% in different CO2 + CO gas mixtures were analysed. The results showed that the metallised burden can be oxidised by CO2 under sufficiently large CO2 partial pressure. In a 50%CO2 + 50%CO gas mixture, Fe was oxidised to FeO. And the reaction started at 718°C, which is much higher than the temperature in the upper shaft of BFs. The metallised burden cannot be oxidised by CO2 in the low temperature zone of BFs. During the descent of the burden, temperature increases and the reduction atmosphere strengthens in an actual BF. The CO2 partial pressure is insufficient to oxidise the metallised burden.

CFD study of hydrogen co-injection through tuyere and shaft of an ironmaking blast furnace

Hydrogen (H2) can be co-injected into the tuyere and shaft into a blast furnace (BF) for reducing CO2 emissions. However, the feasible co-injection schemes and their effects on in-furnace phenomena are not well understood. In this study, a multi-fluid industrial-scale BF model is further developed to investigate the impacts of H2 co-injection through the shaft and/or tuyere on the BF internal state and overall performance in terms of temperature field, H2 and CO utilisation efficiency, and species distributions. The results show that the proposed H2 co-injection through tuyere and shaft allows H2 to be better utilized and the overall BF temperature field can be improved, compared to respective tuyere or shaft injection cases. Further, the effects of high hydrogen injection rate at tuyere (i.e., low hydrogen injection rate at shaft) are studied. It is found that with increasing H2 injection ratio at tuyere, the water gas reaction and water gas shift reaction are intensified; the temperature is decreased and the H2 utilization efficiency is suppressed; the raceway adiabatic flame temperature (RAFT) gradually decreases; the lowest coke rate is 285.8 kg-C/t-HM is found when the distribution ratio of injected H2 is 4:6 at tuyere and shaft, and the highest coke replacement ratio is 4.1 kg-C/kg-H2. Then, the possible operation strategies for H2-rich operation of blast furnaces are explored. This paper provides a cost-effective tool to understand the flow-thermal-chemical behaviours inside a BF when H2 co-injection schemes are employed.

Coarse-grained rCFD-DEM analysis of coke gasification and iron ore reduction in the shaft region of an ironmaking blast furnace

Understanding the fundamentals of iron ore reduction and coke gasification in the shaft region of an ironmaking blast furnace (BF) is the key to improving iron productivity and stability, yet the particle-scale understanding is hindered by the huge computational cost. In this paper, a coarse-grained reacting CFD-DEM (rCFD-DEM) model is implemented to investigate the complex thermochemical behaviours inside a simplified BF shaft. The results show that, in comparison to the CFD-DEM approach, the coarse-grained rCFD-DEM approach can have a similar accuracy but reduces computational cost by ~89.01% in this study. The typical thermochemical behaviours in respective coke and iron ore layers can be captured at particle scale. Then the effect of key operating parameters is studied quantitatively at particle scale. It is indicated that the inlet velocity increasing from 1.7 m/s to 2.3 m/s improves the reduction degree of iron ore by 16%, but the coke consumption is reduced by 5.51%. The operating temperature increasing from 1200 K to 1250 K increases the coke consumption by 44.92%, but the reduction degree of iron ore only increases slightly. When CO mass fraction in the inlet gas increases from 0.25 to 0.30, the coke consumption increases by 12.68% and the reduction degree of iron ore increases by 16.88%. The findings shed light on the fundamentals of coke gasification and iron ore reduction in the BF shafts. • A coarse-grained reacting CFD-DEM model is developed to investigate the blast furnace shaft. • Compared to previous CFD-DEM approach, the approach have a similar accuracy but reduces computational cost by ~89%. • The typical thermochemical behaviours and the effect of key operating parameters are quantified. • The findings shed light on the fundamentals of coke gasification and iron ore reduction in blast furnace shafts.

Towards more efficient control of the ironmaking blast furnace: modelling gaseous reduction of iron ores in H2-N2 atmosphere

Abstract The fraction of hydrogen (H2) in the blast furnace (BF) shaft gas containing a notable portion of nitrogen (N2) is expected to increase. For more efficient control of the BF, it is therefore desirable to conduct more rigorous studies on gaseous reduction of iron ores especially in H2-N2 atmosphere. In this paper, an unreacted shrinking core model (USCM) with multicomponent gas diffusion for iron ore reduction in H2-N2 atmosphere is developed. The resultant nonlinear equations are solved using the 4th order Runge-Kutta method. The present model and the original USCM are compared based on a series of pertinent experimental data.

Reduction of Acid Iron Ore Pellets under Simulated Wall and Center Conditions in a Blast Furnace Shaft

The operational conditions, including temperature and gas composition, vary along the radial position in a blast furnace. Nevertheless, very few studies can be found in the literature that discuss how the reduction behavior of the ferrous burden varies along the radial position. In this study, the effect of the radial charging position on the reducibility of acid iron ore pellets was investigated using a laboratory-scale, high-temperature furnace in CO-CO2-N2 and CO-CO2-H2-H2O-N2 atmospheres up to 1100 °C. The experimental conditions were accumulated based on earlier measurements from a multi-point vertical probing campaign that was performed for a center-working European blast furnace. The main finding of this study is that the pellet reduction proceeded faster under simulated blast furnace conditions resembling those in the center area, compared to the wall area, because of a higher share of CO and H2 in the gas. Therefore, the pellet charging position affects its reduction path in a blast furnace. Additionally, it was shown that the presence of H2 and H2O in the reducing gas enhanced the progress of reduction reactions significantly and enhanced the formation of cracks slightly, both of which are desirable in blast furnace operation. The reducibility data attained in this study are important in understanding how temperature and gas composition is connected to the reduction degree under realistic process conditions.

Computer modelling of burden distribution in the blast furnace equipped by a bell-less top charging system

ABSTRACT This article describes the simulation method for layering the components of the charge in the blast furnace, including the particle size distribution and gas flow distribution of bell-less top charging systems in blast furnaces. The Burden Distribution application, which simulates the charge in blast furnaces operated by the company Třinecké železárny (ironworks) to optimize the production of pig iron, applied this simulation method. Based on the parabolic trajectory of the material falling from the tilting chute of the bell-less top charging system, the method is calculating the profile of individual charge layers. The material forms after impact according to known angles of repose, segregating into individual granulometric size fractions. The data incorporated into the simulation enables the estimation of charge and gas flow distribution along the radius of the blast furnace shaft. The article presents the used mathematical models and equations, including algorithms of the simulation.

Model for the approximate assessment of nitrogen content in swollen reduced iron ore from single measurements

A method of calculation has been derived to assess the nitrogen estimated content in iron reduced samples. The method is based on the review of observations and laboratory measurements of relationships between the rate of reduction and the corresponding metallic iron formation during the reduction process. The metallic iron formation has been calculated from relationships that apply to a wide variety of types of ores undergoing reduction under a nitrogen-containing gas mixture in proportions above 50% by volume. The empirical correlations found between the rates of metallization, the sample swelling index, and the equilibrium nitrogen solubility in iron can be used for determined the approximate final content of nitrogen in the reduced samples from the estimated and measured final volume of the reduced specimens. It is necessary to have an accurate analysis of the starting sample as well as the reducibility information.
 Keywords: Iron ore, nitriding, catastrophic swelling, rate of metallization, reduction degree.
 [1]M. Kumar, B. Himanshu & S. Kumar. “Reduction and Swelling of Fired Hematite Iron Ore Pellets by Non−coking Coal Fines for Application in Sponge Ironmaking”. Mineral Processing and Extractive Metallurgy Review- MINER PROCESS EXTR METALL REV. 34. 10.1080/08827508.2012.656776. 2012.
 [2]I. Mikko, M. Olli, A. Tuomas, V. Ville-Valtteri, K. Jari, P. Timo & F. Timo. “Dynamic and Isothermal Reduction Swelling Behaviour of Olivine and Acid Iron Ore Pellets under Simulated Blast Furnace Shaft Conditions”. ISIJ International. 52. 1257-1265. 10.2355/isijinternational.52.1257. 2012.
 [3]M. Kumar. “Study of reduction kinectics of iron ore pellets by noncoking coal”. Thesis of Master. National Institute of technology, Rourkela. 2009.
 [4]O. Dam. “The Influence of Nitrogen on the Swelling Mechanism of Iron Oxides During Reduction”. PhD Thesis .Univ. of London. 1983.
 [5]O. Dam and J. Jeffes. “Model for the Assessment of Chemical Composition of reduced iron ores from single measurements”. Ironmaking and Steelmaking Journal. Vol. 14, N`5. 1987.
 [6]O. Dam. “Efecto de la descomposición de gas de amoniaco (NH3) sobre el hinchamiento de óxidos de hierro durante reducción”. UCT Journal. Vol 100, 24. May 2020.
 [7]R. Agarwal and S. Hembram. “To Study the Reduction and Swelling Behavior Iron Ore Pellets”. BSc. Department of Metallurgical and Materials Engineering National Institute Of Technology, Rourkela. May 2013
 [8]Z. Chen , C. Zeilstra , J. Van der Stel , J. Sietsma & Y. Yang. “Review and data evaluation for high-temperature reduction of iron oxide particles in suspension”. Ironmaking & Steelmaking. Vol. 47. N°7. pp. 741-747. 2019.

Coke Gasification in Blast Furnace Shaft Conditions with H2 and H2O Containing Atmospheres

Most of world steel in 2018 has been produced from virgin iron ore via the blast furnace (BF)—basic oxygen furnace route. Therewith the BF is one of the most important unit processes in worldwide steel making. Among others, energy efficiency of the BF is dependent on coke reactivity. Coke gasification occurs via solution‐loss reactions either with CO2 or H2O. Herein, the gasification of coke is studied in CO–CO2–H2–H2O–N2 atmosphere simulating the BF conditions. The simulated atmospheres are based on the measurements from an actual BF. This research studies the effect of the composition of the BF atmosphere representing conditions near the wall as well as at the center and influence of the H2O content on coke gasification under simulated BF conditions. It is found that the location plays a role in coke gasification: wall atmosphere yields higher coke gasification compared with center. Dynamic tests show that introduction of H2 and H2O in gas atmosphere fastens coke gasification by +119% at temperature range between 800 and 1200 °C in wall conditions. When H2O is present in gas atmosphere, the mass loss of coke is also greater in both wall and center conditions.

Prediction of the cohesive zone in a blast furnace by integrating CFD and SVM modelling

ABSTRACT High efficiency and clean emission operation of a blast furnace are mainly determined by its operating stability, which is closely related to the position of the cohesive zone (CZ) in the blast furnace. In order to monitor the CZ position in real time, a prediction model of the CZ was proposed by combining an off-line computational fluid dynamics (CFD) calculation and support vector machine (SVM) modelling. An axisymmetric two-dimensional steady-state CFD model was established to simulate the fluid flow, heat and mass transfer in the blast furnace shaft. The sample dataset of the CZ information was established based on the CFD off-line calculation, and the prediction of the CZ position was realized by SVM modelling. The results show that the established model can predict the CZ position in real time with high accuracy, providing effective guidance to the blast furnace operation and control.

Reduction of Iron Ore Pellets, Sinter, and Lump Ore under Simulated Blast Furnace Conditions

A blast furnace (BF) is the dominant process for making iron in the world. The BF is charged with metallurgical coke and iron burden materials including iron ore pellets, sinter, and lump ore. While descending in the BF the charge materials reduce. The iron‐bearing materials should reduce fast and remain in the solid form until as high a temperature as possible to ensure reaction contact with reducing gas and iron oxides. Herein, the reducibility of the iron ore pellet, sinter, and lump ore in the BF shaft are focused on. The experiments are conducted isothermally with a blast furnace simulator (BFS) high‐temperature furnace at four different temperatures (700, 800, 900, and 1000 °C) for 300 min. The experimental atmosphere consists of CO, CO2, H2, H2O, and N2 simulating the conditions in the BF shaft. It is found that lump ore has lowest reduction rate in all test conditions, and at lower temperatures iron ore pellets reduce faster than sinter, and this is reversed at higher temperatures. Furthermore, the reduction rate of sinter and iron ore pellets begins to resemble each other at higher temperatures.

Upgrading of Blast Furnace Sludge and Recycling of the Low-Zinc Fraction via Cold-bonded Briquettes

Depending on the operation of the blast furnace (BF), the main outlet of zinc from the furnace is more or less via the BF dust and sludge. As the dust is recycled to the BF, the sludge has to be de-zinced prior to recycling to prevent the accumulation of zinc in the BF. De-zincing and recycling of the low-zinc fraction via sinter have been reported. However, no research concerning recycling of upgraded BF sludge via cold-bonded briquettes has been performed. In the present study, a fine-grained BF sludge with low zinc content, generated by a BF operating on a ferrous burden of 100% pellets, was upgraded using the tornado process. The process simultaneously dried and separated the BF sludge into a high-zinc and a low-zinc fraction. The feasibility of recycling the low-zinc fraction to the BF using cold-bonded briquettes was studied on a laboratory-scale BF shaft simulator. On comparison with a reference briquette, the experiments indicated that 10 wt% of the upgraded BF sludge can be added to the briquette without negatively affecting the reducibility. Higher additions were found to render the briquette less reduced compared to the reference under test conditions corresponding to the central part of the BF. The strength of the briquettes was not compromised with the addition of the upgraded BF sludge, and a decision to study the briquettes in the LKAB experimental blast furnace was made in order to evaluate the behavior under actual BF conditions.

Lignin from Bioethanol Production as a Part of a Raw Material Blend of a Metallurgical Coke

Replacement of part of the coal in the coking blend with lignin would be an attractive solution to reduce greenhouse gas emissions from blast furnace (BF) iron making and for obtaining additional value for lignin utilization. In this research, both non-pyrolyzed and pyrolyzed lignin was used in a powdered form in a coking blend for replacing 5-, 10- and 15 m-% of coal in the raw material bulk. Graphite powder was used as a comparative replacement material for lignin with corresponding replacement ratios. Thermogravimetric analysis was performed for all the raw materials to obtaining valuable data about the raw material behavior in the coking process. In addition, chemical analysis was performed for dried lignin, pyrolyzed lignin and coal that were used in the experiments. Produced bio cokes were tested in a compression strength experiment, in reactivity tests in a simulating blast furnace shaft gas profile and temperature. Also, an image analysis of the porosity and pore shapes was performed with a custom made MatLab-based image analysis software. The tests revealed that the pyrolysis of lignin before the coking process has an increasing impact on the bio coke strength, while the reactivity of the bio-cokes did not significantly change. However, after certain level of lignin addition the effect of lignin pyrolysis before the coking lost its significance. According to results of this research, the structure of bio cokes changes significantly when replacement of coal with lignin in the raw material bulk is at a level of 10 m-% or more, causing less uniform structure thus leading to a less strong structure for bio cokes.

A Visualization Technique to Predict Abnormal Channeling Phenomena in the Blast Furnace Operation

An uneven gas distribution through the burden layers inside a blast furnace (BF) results in abnormal gas resistance or pressure changes. Rapid variations in the abnormal gas resistance will lead to the occurrence of channeling. A visualization technology mainly made of pressure distribution was developed to predict BF channeling phenomena in this study. The real-time data of BF shaft pressure was used to create a 3D visual model by neural network algorithms and 3D real-time BF pressure changes were observed. The root mean square deviation (RMSD) of the BF shaft pressure was used as an index to set up the predicting criteria of channeling occurrence with the opening of BF Annular Gap Element (AGE), and a predicting system based on the criteria was built. The two criteria for the channeling alarm are the RMSD of the BF shaft pressure (> 0.15 kg/cm2) at the upper two levels, and the AGE opening being greater than 60%. This system has been installed in the China Steel Corporation (CSC) BFs, and the test results showed that a prediction can be obtained 8 to 16 min ahead of channeling allowing sufficient time for the operator to adjust the BF operation in order to avoid the occurrence of channeling.

A comparison of partially burnt coal chars and the implications of their properties on the blast furnace process

Blast furnace coal injection is a vital part of modern ironmaking, reducing the amount of coke reductant required in the process and increasing its efficiency. However the injection of different coals or their blends, into the raceway formed by the hot blast, has technical issues due to the very short particle residence times and the limited availability of oxygen in this region. This makes complete burnout difficult and limits the range of coals suitable for this application, leading to partially burnt chars being carried out of the raceway into the blast furnace shaft and potentially into the off-gas system.This paper explores the fate of these chars, from a range of different coals, looking at how this influences the selection for injection and the implication of these on the blast furnace. In particular, we have looked beyond the limitations of selecting coals based on proximate analysis alone by examining in more detail other physical and chemical properties and their potential effect on the process. A drop tube furnace (DTF) has been used to synthesise chars in a high heating rate environment, and although burnout and volatile loss values suggest suitability of some coals for blast furnace injection, additional problematic effects have been identified and measured such as char swelling and agglomeration which may impact the gas permeability of the furnace. A TGA/DSC has been used to measure the gasification of chars by the Boudouard reaction and compare the thermal impact of more reactive samples.While other studies have concentrated on the combustion of injection coals to determine their suitability, this one focuses on the implications of the partially burnt chars formed by incomplete reaction in the raceway.

Development of technology of pulverized coal injection in Ukraine’s blast furnaces in variable liquid and gas dynamic conditions

The aim of the work is to study the features of the use of pulverized coal (PCI) in the conditions of the blast furnace (BF) No. 5 of Metinvest Holding Ltd (Ukraine). The complex for the preparation and use of pulverized coal includes: a coal unloading and storage area; coal mixing section; coal sampling unit; plot of coal sorting and preparation; installation of drying and grinding coal raw materials, installation for the injection of pulverized coal into the BF. It is shown that the use of rational modes of loading and forming portions of the charge, the choice of rational slag mode allowed to increase the annual consumption of pulverized coal on average up to 130 kg / t of pig iron even in the conditions of variable load of BF and when working on coke of reduced quality. During the research, an operational monitoring of the condition of the lining of the BF shaft was carried out using the indications of the thermocouple of the lining and the body of the refrigerators. The determination of the thermal loads of the cooling system made it possible to develop measures to adjust the distribution of the charge components along the radius and circumference of the furnace. The temperature of the peripheral gas flow along the entire height of the furnace is reduced by an average of 13%, the irregularity of the peripheral temperature is reduced by 11%. The stability of the cooling system and the smooth operation of the blast furnaces.

Introduction of pulverized-coal injection at Yenakiieve Iron and Steel Works

The introduction of pulverized-coal injection at Yenakiieve Iron and Steel Works in 2016 is described. The state of the lining of the blast-furnace shaft and hearth is analyzed. Requirements regarding the charging conditions are proposed so as to improve the durability of the cooling system and ensure accident- free furnace operation.

Coke Reactivity in Simulated Blast Furnace Shaft Conditions

Despite the fact that H2 and H2O are always present in the gas atmosphere of a blast furnace shaft, their role in the solution-loss reactions of coke has not been thoroughly examined. This study focuses on how H2 and H2O affect the reaction behavior and whether a strong correlation can be found between reactivity in the conditions of the CRI test (Coke Reactivity Index) and various simulated blast furnace shaft gas atmospheres. Partial replacement of CO/CO2 with H2/H2O was found to significantly increase the reactivity of all seven coke grades at 1373 K (1100 °C). H2 and H2O, however, did not have a significant effect on the threshold temperature of gasification. The reactivity increasing effect was found to be temperature dependent and clearly at its highest at 1373 K (1100 °C). Mathematical models were used to calculate activation energies for the gasification, which were notably lower for H2O gasification compared to CO2 indicating the higher reactivity of H2O. The reactivity results in gas atmospheres with CO2 as the sole gasifying component did not directly correlate with reactivity results in gases also including H2O, which suggests that the widely used CRI test is not entirely accurate for estimating coke reactivity in the blast furnace.