POVEROMO INTERNATIONAL SYMPOSIUM (8TH INTL. SYMP. ON ADVANCED SUSTAINABLE IRON AND STEEL MAKING)

KEYWORDS: Banking, Burden, Oxy lance, Start Up, Ramp Up. ABSTRACT Blast Furnace operation is a continuous process and goes on till the end of its campaign except for some short shut down for maintenance or repair work. Banking of a blast furnace is like the operation of banking a fire and it is covered with fuel to restrict air preserving it for future use during furnace start up [1]. Banking of a blast furnace is generally done to take care for any unwanted situation. Nowadays most of the blast furnace operators prefer to blow down the furnace instead of banking because starting up of a banking furnace is associated with more risk and always unpredictable than a blowdown of a blast furnace [2]. Blowdown of a blast furnace needs a lot of preparatory activities which normally take time, but E & C Blast furnace of Tata Steel had to be banked on urgent basis initially for 1 month in March’20 due to unavoidable circumstances of COVID’19. Later banking period was extended to 3 months due to increasing trend of COVID’19 pandemic. Startup of a banking furnace, always unpredictable in nature, requires lot of preparation and the task becomes more challenging when banking period is extended [3]. Since a banking blast furnace revival is a hazardous activity, generally expertise with sound technical knowhow on banking blast furnace revival is required. For reviving a banked blast furnace, usually technology like Oxy Fuel lance or Durfee Method is applied [4]. E & C both blast furnaces were banked with calculated amount of burden for 1 month and revived successfully with help of in house designed Oxy Lance even it was extended to 3 months. For reviving a banking blast furnace, hot blast temperature also plays a very important role. Hot blast is generated through heating cold air by a cyclic process namely” On Gas & On Blast” in a blast furnace stove. A certain degree of hot blast temperature is required to burn the fuel inside the furnace which was charged during banking. E & C Blast furnace achieved desired degree of hot blast temperature by in-house designed tri-axial lance for initial and faster heating of stove with combination of Coke Oven Gas, Blast Furnace Gas and Compressed Air. This paper will describe in detail revival process of E & C blast furnace of Tata Steel.

As has shown long-term experiment of Institute of metallurgy of the Ural Branch of the Russian Academy of Sciences, at the solution of practical problems of ferrous metallurgy the increasing role is played by the information systems which basis are mathematical models of the physical, chemical and thermal processes proceeding in metallurgical units [1]. It is known that the cohezive zone in the blast furnace will be formed as a result of a softening of an iron ore component of burden, coke is in solid state. This zone makes limiting impact on productivity of the blast furnace [2]. Location and a form of a cohezive zone substantially is determined by character of unevenness of the temperature field depending on system of loading, the location of the tuyere center, a profile of shaft and change of gas dynamic resistance by height of the blast furnace; in temperatures of a softening and melting of the iron ore material, depending on extent of reduction [3]. Results of calculations of location and form of a zone of a cohezive in the blast furnace for iron ore materials with different metallurgical characteristics are given.

Carbothermic reduction of fine steel sludge (FSS-LD) and coarse steel sludge (CSS-LD) occured from Linz Donawitz steelworks in a Brazilian semi-integrated steel plant. These processes were carried out prior to characterization, for which, they determined high levels of iron content (51.54 - 77.53%) and zinc content (0.49 - 1.69%), as well as, a little specific carbon content (0.0215 - 0.0350%). Morphology shown by these residues are made up of globular aggregates of metallic iron intergrown with crystals of iron oxides and zinc oxide with particle sizes between 0.12- and 0.15-mm observable through a Scanning Electron Microscope (SEM). Thermal characterization via DTG-DSC-TG at 1000°C prior to carbothermic reduction Mass losses of 92.57% were observed for the FSS - LD sample and 97.43% for the CSS - LD sample

Since 2008, four Japanese blast furnace steelmakers and one engineering company have been working on an innovative ironmaking process project named COURSE50. The main research activities of the project consist of two parts. One is the development of hydrogen utilization technology for iron ore reduction using coke oven gas that contains a large amount of hydrogen. The other is the development of CO2 capture technology from blast furnace gas by unused wasted heat within steelworks. By using these major technologies, the project aims to cut CO2 emissions from steelworks by 30%. The project has successfully completed STEP1(2008-2012), the development of basic technologies and STEP2(2013-2017), the development of comprehensive technologies. As a result, the carbon consumption in the blast furnace was reduced by 10% by the developed reaction-controlling technology. We also developed high-performance chemical absorption and physical adsorption methods to reduce 20% of CO2 emitted from steel works.

The last decade was a turbulent for the steel industry. The reorganization of steel industry across borders has progressed and the increased demand for steel products has made the price of raw materials such as iron ore and metallurgical coal more volatile than ever. Ironmaking technology division in JAPAN has been exposed to global competition and has tried to cope with these changes and to increase its international competitiveness by developing such technologies as utilization of lower grade raw materials, productivity enhancement, measures for energy conservation and reduction of CO2 and NOx emission and so on. This paper describes the recent progress in ironmaking technologies in JAPAN.

Saving carbon dioxide emission is essential to produce environmentally friendly steel especially, decreasing its amount from blast furnace process is important. Not only faster reduction of iron ore but also the acceleration of carburizing and melting of reduced iron is the method to achieve it. Understanding ash behavior in coke is important to control carburization. In this study, concentration behavior in ash compounds on the surface of coke by gasification under blast furnace condition and melting behavior of iron tablet by the direct contact with coke were examined. Furthermore, in-situ observations of melting behavior of coke-iron composite and effect of de-ash treatment was carried out.
Ash concentrates on the surface of coke by gasification, and the coverage ratio of ash on the coke surface increases with increasing coke reactivity. Melting of iron by carburization from coke proceeds at lower temperature when coke reactivity is high. However, the effect of ash coverage ratio on this behavior is much higher than that of coke reactivity and an increase in ash coverage ratio leads to preventing carburization and melting of iron. SiO2 in ash reduces to Si by carbon, and it alloys with metallic iron. It can be concluded that Si prevent to melt iron.

The steel industry occupies for about 14% of CO₂ emissions in Japan, and it is necessary to reduce CO₂ especially, sintering and blast furnace processes occupies the majority for CO₂ emission from steel industry. As blast furnace exhaust gas is used in the downstream process, the target of our study is to reduce CO₂ from the sintering process. Most of CO₂ emitted from the sintering process comes from coke breeze combustion. It is effective to replace coke breeze with low oxidation iron or biomass as bonding agent. Regarding the former, Fujino et al. examined a method for promoting oxidation of metallic iron and ferrous (Fe²⁺) oxide.[1]-[4]
In the past, on the other hand, there are few previous studies on the latter. Kawaguchi et al. examined using biomass char sinter pot test[5], and resulted in that shortened sintering time due to the high burning rate of biomass char and maintained product yield by sieving and using large particle char. However, there is no mention of other sintering operating factors or their effects on sinter product quality.
Therefore, in this study, in order to explore the effective use of biomass char, we will examine the NOx emission[6] and sinter quality with its combustion characteristics and heat profile in sinter packed bed, and PKS char was used as biomass char, and its combustion characteristics were investigated by particle size. As a result, it was confirmed that the finer the PKS char showed the faster the burning rate and the lower the NOx conversion rate.
It is suggested that higher combustion rate caused lower oxygen partial pressure in the combustion film near the char particle. Then lower oxygen partial pressure suppressed oxidation reaction of Nitrogen component in the char.

The blast furnace operation and economics are significantly influenced by the performance of burden materials descending in the furnace shaft. Changes in burden permeability and reducibility relates to the degree of indirect reduction, and therefore reductant requirement and iron productivity. Chemical composition, and physical and metallurgical properties of burden materials are determined using standard (ISO) test procedures. Tests are performed on specific material size distributions, and mostly at constant temperatures and gas compositions representative of typical blast furnace zones.
Materials are directly compared on qualities derived from standard tests. However, the marginal impacts on economic and emissions performance when substituting burden materials are not easily determined from standard material qualities. Contributing to inaccuracies are the transient nature of temperature and gas composition in actual processes, differences in material size distribution, and effects of other material properties.
The softening, melting, and dripping behaviour of materials at transient conditions, typical for blast furnaces, are determined in high-temperature tests [1]. In this investigation, such tests are performed on iron ore sinters, pellets, and lump ores using the test procedure developed by Ritz et al. 1998 [2]. A material sample, normally -12.5+10 mm, is placed under load and electrically heated while varying gas mixtures are injected over time to resemble the changing conditions down the blast furnace shaft.
Sample temperature, pressure drop, compaction, and the outlet gas composition are continuously measured during tests. Results derived include the location of the expected softening and melting points in the blast furnace in terms of temperature and time (i.e. location and thickness of the cohesive zone), and the degree of reduction over time. These tests are believed to more accurately indicate the amount of indirect reduction to be expected in the blast furnace and therefore the impact on the reductant requirement when comparing burden materials.
In this work, the material qualities determined in standard (ISO) tests were related to the actual performance in the blast furnace derived from high-temperature tests by using reaction kinetics and thermodynamic modelling. The purpose of this being to more accurately estimate blast furnace performance from more readily available burden material qualities.
Aspects investigated include: (1) softening and melting behaviour in relation to the degree of reduction and chemical composition during processing, (2) the amount of indirect reduction achieved at the softening point (start of cohesive zone) relative to a reducibility index value for a material with size distribution of interest, and (3) the impact that percentages of different materials in the burden has on the overall blast furnace performance.

Over the past several hundred years, ironmaking has evolved from blast furnace iron production using mainly natural lump and initially charcoal and then coke to the present day where the blast furnace (BF) is still the dominant ironmaking process but based on using a high percentage of agglomerates (sinter and/or pellets) and coke supplemented by injected reductants (pulverized coal, natural gas, fuel oil, coke oven gas, plastics). The emerging ironmaking process is shaft furnace direct reduction (DR) based on mainly pellet use with natural gas as the reductant. The technological developments for agglomerates, coke and injectants will be reviewed. In the quest for development of sustainable ironmaking, the development of alternative iron bearing materials (ore/coal composites, ore fines, etc) and alternative reductants and injectants (H2, biomass, etc) will be previewed.

The blast furnace process is based on carbon reduction and a coke base is a necessity to sustain reduction through the cohesive zone, melting of the ferrous and separation into carburized hot metal and slag[1]. Partly replacing carbon with hydrogen as a sustainable source of energy and reductant has been proven [2] but when and where will the boundaries of the current process occur and can they be stretched. Though hydrogen advantages in the dry part of the shaft are clear, the cohesive zone becomes a first bottle neck, as will be shown through calculations. On the other hand, the water gas shift reaction proofs supportive.
Approaching it from a different angle, Direct Reduction is seen as an existing process capable to switch over to complete hydrogen usage for sustainable ironmaking [3]. Aside from the process scale, this approach requires a different view on burden composition and quality and the efficient use of DRI in the subsequent steelmaking process needs further development. Current bottle necks and approaches to solve will be discussed. In the end combination of both integrated as well as DR steelmaking will benefit both technologies

Based on the result of theoretical analysis, it has been shown that injection of pulverized coal supports process conditions either to provide higher smelting rate or achieve minimum coke specific consumption. In case of coke and natural gas replacement, two conflicting factors can be observed: gas amount per minute is reduced thus having a favorable effect on gas dynamics both at upper and lower zones of the furnace; porosity is decreased in slag formation zone. It determines extreme correlation between PCI (pulverized coal injection) consumption and blast furnace performance. It has been established that increasing ratio of PCI to natural gas (NG) consumption is followed by lower coke and total carbon in fuel specific consumption at slowdown. High smelting rate can be achieved with this ratio within the range of 2.0-2.5. Mathematical modelling also revealed that the replacement coefficient of coke by NG increases in average by 0.09 kg of coke per Nm3 of NG with PCI rate with increase accompanied by simultaneous reduction in NG rate. The overall consumption carbon consumption was reduced despite the difference in carbon amount entering the furnace with PCI and NG.

Timely and complete taping of hot metal and slag is the main precondition of blast furnace intensive operation. Irregular taping leads to fluctuation of the level of liquid products in the furnace hearth, change in rate of material charging to the furnace and variations in a burden residence time in the furnace. Also it effects the thermal state of the furnace and chemical composition of the hot metal and slag. Ratio of tapped hot metal and slag is determined by physical properties of slag, diameter and length of hot metal taphole. Analysis of NTMK-Evraz blast furnaces operation showed significant fluctuations of this ratio. At average slag volume between 340-360 kg/thm the actual range of slag volume changes from 200 to 850 kg/thm. The fundamentals of mechanics of fluid and gases were applied to study the problem and laminate flow of hot metal and slag was assumed for the taphole. The ratio of the metal and slag mass in the taphole and hot metal and slag velocities were described as a function of slag parameters and taphole geometry. This approach allowed to derive numerical relationship between volumes of tapped hot metal and slag, slag viscosity and taphole design. Results of mathematical modeling were confirmed by actual performance parameters of NTMK-Evraz blast furnaces. It was found, that increase in slag to hot metal ratio led to the reduction in blast furnace productivity and reduction in vanadium partition to hot metal.

Industrial revolutions mark a great leap of technologies that changes the productive paradigm, that change is known as industrial revolutions [1] [2]. Industry 4.0 has changed the way industry operates and manages its operations, new technologies are being applied to increase productivity, reduce losses utilizing information systems and communication based on the Internet of Things (IoT). [3] In this context, new systems were adopted to facilitate the management of industrial processes, for those processes which have interaction between different sectors in the production operations, integrated systems emerge as a solution to facilitates communication and time reduction to collect data. Due to automation, there is an increase in the control over operational variables.
The present work presents solutions based on the concept of industry 4.0, especially integrated systems for the management of by-products and waste produced in a steel plant. The Online Productive Process Monitoring (OPPM) and the By-products Management Integrated Systems (BMIS) are automatic solutions applied for by-products management. The first one shows the by-products consumption in different sectors. The monitoring is online and on-demand. The Waste Collections Monitoring Points (WCMP) facilitates the logistics of waste collection.

The mass transfer rate between different phases such as solid/liquid and liquid/liquid is important to control the slag/metal reaction in the pyrometallurgy field. The solid/liquid mass transfer rate was changed by the suspension patterns of sedimentary particles [1, 2] and floated ones [3, 4] in an impeller stirring. When the stagnant particles partially suspend into liquid, the mass transfer rate began to enhance rapidly, and it was promoted by the collision of lighter density of particles with the impeller and the irregular dispersion into the liquid phase. The liquid/liquid mass transfer rate was also affected by the collision of lighter density of liquid with the impeller [5, 6]. The liquid/liquid flow characteristics of impeller stirring were investigated by a two-dimensional PIV experiment and a computational fluid dynamics (CFD) technique [7] and the space-averaged velocity were found to irregularly enhance when the lighter liquid began to collide with the impeller. The particle penetration depth enhanced the solid/liquid mass transfer rate in the particle blowing technique [8]. In this study, based on the above results of cold model experiments and CFD, the relationship between the mass transfer rates between different phases and suspension pattern was adjusted as a whole.

The mass transfer rate between different phases such as solid/liquid and liquid/liquid is important to control the slag/metal reaction in the pyrometallurgy field. The solid/liquid mass transfer rate was changed by the suspension patterns of sedimentary particles [1] and floated ones [2, 3] in an impeller stirring. When the stagnant particles partially suspend into liquid, the mass transfer rate began to enhance rapidly, and it was promoted by the collision of lighter density of particles with the impeller and the irregular dispersion into the liquid phase. The liquid/liquid mass transfer rate was also affected by the collision of lighter density of liquid with the impeller [4, 5]. The liquid/liquid flow characteristics of impeller stirring were investigated by a two-dimensional PIV experiment and a computational fluid dynamics (CFD) technique [6] and the space-averaged velocity were found to irregularly enhance when the lighter liquid began to collide with the impeller. The particle penetration depth enhanced the solid/liquid mass transfer rate in the particle blowing technique [7]. In this study, based on the above results of cold model experiments and CFD, the relationship between the mass transfer rates between different phases and suspension pattern was adjusted as a whole.

The HIsmelt ironmaking technology is operating successfully in China and its unique flexibility to smelt a wide range of raw materials offers several pathways to sustainable steelmaking. The HIsmelt technology was developed in Australia from 1990 to 2016 and has been owned and operated in China by Molong Petroleum Machinery Ltd since 2016. HIsmelt produces high quality liquid pig iron that can be used in electric arc furnaces (as hot metal or cold pigs) or oxygen steelmaking furnaces (as hot metal). The pathways to sustainable steelmaking include:  (1) elimination of CO2 emissions via the injection of sustainable biomass and/or carbon capture and sequestration, (2) consumption of DRI produced via hydrogen reduction and/or biomass reduction, (3) consumption of local iron ore resources not suitable for use in blast furnaces or DRI furnaces, and (4) production of hydrogen via electrolysis using excess power from the waste gas. The HIsmelt plant currently operating in China has a 6m diameter hearth and produces approximately 600,000 tonnes per year of hot metal from directly shipped iron ore fines. The production from a 6m module could be increased to 1,500,000 tonnes per year of hot metal when smelting DRI. A larger module HIsmelt plant has been designed that could double the production of hot metal from a single vessel i.e. up to 3,000,000 tonnes per year of hot metal.

The modern blast furnace performance has achieved a high standards in the production technology, development of its raw materials and fuel facilities, mathematical modelling of its processes, as well as in the control, automation and optimization systems complexity and appication. To control successfully blast furnace operation mathematical models and subsystems of gas and burden heat exchange, materials softening and reduction of chemical elements, gas- dynamics, melting primary slags formation, liquids and materials movement along the furnace height were developed and applied to several blast furnaces. Numerous laboratory, pilot plant and actual operation studies were conducted to enrich the understanding of blast furnace process phenomena and to obtained reliable coefficients of the mathematical models. Various thermal sensors, radioisotope and laser profile meters and gas temperature and composition probes above level of charge materials are installed and used for this purpose.
As a result of these studies and modelling it was found that position of the cohesive zone has a profound effect on stable blast furnace operation at low levels of coke and PCI/NG rate and hot metal silicon. It was shown that the boundary of cohesive zone more accurately determined not by temperature isotherm, but viscosity isokoms: 18-20 pois for upper level and 6-7 pois for lower level. It was also found that FeO fluctuations in primary slags formed from low basicity/acid pellets (up to 40%) and high basic sinter (less than 15%) determine the volume and extend of liquids in blast furnace, limits the pressure drop and filtration intensity. Results of this work are implemented for NLMK, CherMK-Severstal, Tulachermet, Azovstal, Alchevsk and Zaporozhstal Iron & Steel Works in Russia and Ukraine.

The maximum productivity  of blast furnace very much depends on optimal configuration of the cohesive zone: minimum thickness and the best melt filtration into the lower level. Developed mathematical model allows an assessment of the position and shape of the cohesive zone in a blast furnace and identification of a rational configuration for this zone on the basis of readily available information regarding the blast furnace in the baseline period. The model also permits to resolve the design problems by variation in the furnace parameters. Modeling results are outlined for the baseline and design periods. Results of the mathematical modelling are confirmed by operational performance of Magnitogorsk Iron & Steel Works.

In order to reduce the fuel rate of blast furnace and promote green development, Shougang Jingtang Steel company has built two straight grate indurating machines with productivity of 8 million tons of pellets. In this paper, the production technologies of self-fluxed pellets with hydrated lime were studied successfully on the indurating machine. Hydrated lime has a good binder property, decrease the amount of bentonite and obtain low silica pellet. The basicity of pellet is 1.15 and SiO2 content is 2.0%. The low silica self-fluxed pellets were used in the three large blast furnaces with 5500m3 in Shougang Jingtang, the proportion of pellets in burden was increased from 28% to 55%, slag rate of blast furance was decreased from 280kg/tHM to 215kg/tHM, the fuel rate was decreased from 500kg/tHM to 480kg/tHM.

Fe content in hematite ore is gradually decreasing. The usage low grade iron ore in sintering process increase the volume of a bonding agent in order to maintain the yield and the strength of sinter. However the usage of a bonding agent causes more Carbon dioxide emissions.
Therefore, a magnetite ore has been focused because it can perform magnetic separation and can produce a large amount of oxidization heat. It is because reduction of gangue quantity by magnetic separation makes it possible to produce low slag sintered ore with good reducibility and utilization of oxidizing heat is expected to reduce use of bonding agent. Hence, there are many studies on the oxidation of magnetite. [1][2]. However, despite important reaction as well as oxidation of magnetite, the details of the assimilation of magnetite have not been elucidated. In order to utilize the magnetite ore in the sintering process in the future, it is indispensable to elucidate the mechanism of assimilation of magnetite ore and explore appropriate raw material design. In this report, we introduce the results of a fundamental study on assimilation of magnetite ore and limestone.
In this study, a cylindrical tablet hat was modelled and the adhesive layer of a pseudo particle was prepared and heat treated in the air. As a result of observation of this tablet, it was confirmed that the assimilability of magnetite ore varies depending on the particle size of limestone. Magnetite ore blended with fine grain limestone had higher strength of sinter ores than magnetite ore mixed with coarse grain limestone due to its small pore diameter.

Reduction in heat losses to the cooling system, increase in CO gas utilization, achieving maximum possible blast temperature and top gas pressure and optimum level of Si in hot metal are the main technological drivers to reduce coke rate at NLMK (Novo-Lipetsk Iron & Steel Works) operating conditions. Possibility of reduction in energy and fuel consumption by increase in total iron in iron bearing materials are very limited because of smaller size of concentrate for pelletizing and sintering increases concentrate production cost. Also the higher total iron in concentrate leads to the reduction in volume of liquid phase during sintering and pelletizing and as a result – to reduction of their strength.
Usage of higher quality coke with CSR 60-65% allowed increase in blast furnace process intensity, reduction in specific heat losses, increase in CO utilization and better utilization of higher top gas pressure. As a result the average coke rate for all 5 blast furnaces at NLMK was reduced to 340 kg/thm.

The standard physical and metallurgical tests are designed to differentiate between iron bearing materials. The standard tests prescribe the equipment and test conditions to compare test results across laboratories. Standard tests are widely accepted and used by suppliers and consumers of the materials for commercial purposes and process control. The conditions in blast furnaces and direct reduction processes are dynamic while the standard tests subject the iron bearing material to fixed conditions, making it difficult to relate the impact of standard properties on process performance. [1]
The ISO 3271 standard specifies a method for evaluating the resistance of iron ores to size degradation by impact and abrasion. ISO 3271 prescribes 200 revolutions in a tumble drum to obtain the tumble index (TI), the size degradation Kumba Lump ore from load port to discharge port was correlated with the number of revolutions needed in the ISO tumble drum to obtain similar degradation.
ISO 4696 and ISO 11257 standards are used to evaluate the degree of size degradation of iron ores due to low temperature reduction-disintegration in blast furnaces and direct reduction processes respectively. The use of isothermal reduction does not reflect the dynamic conditions in the processes and the reduction disintegration index (RDI) does not always reflect the actual size degradation [1][2]. The ISO tests are done on one size fraction, and the reduction disintegration size fractions experience are different. The effect of test temperature and size fraction on reduction disintegration were evaluated.
ISO 4695 and ISO 7215 standards are used to evaluate the relative reducibility of iron ores under blast furnace conditions. The standard tests are done on the 10 to 12.5 mm size fraction or on the 18 to 20mm size fraction, depending on which of the two ISO standards are used. The result is expressed as the reducibility index (RI). The rate at which oxygen can be removed from the ore is dependent on the available surface area - coarser particles will be reduced at a lower rate than finer particles. The actual size fraction of the lump ores used in the blast furnace is around 6.3 to 40mm, the mean reducibility of the lump ore considering the particle size distribution were investigated.
The relevance of physical and metallurgical properties of Kumba Lump Ore on the performance in practice were investigated.

In the continuous casting of steel, the rotary or linear electromagnetic stirring were generally used to improve the internal quality of billets, bloom and slabs by generating horizontal rotary motion inside the casting billet, by promoting heat dissipation and temperature homogenization, thereby increasing the equiaxed grain ratio[1] and refining grain size[2], etc. However, in the final solidifying zone of special steel billets, e.g. the stainless steel, bearing steel and nickel-based steel, the poor fluidity and feeding ability of molten metal could not be improved by the horizontal rotary motion inside the casting billet, so that the centre of special billets usually have some central band defects which are difficult to eliminate in the subsequent rolling process, such as element segregation, porosity, shrinkage cavity, cracks and so on.
In this paper, the solidification structure of special steel billets were investigated under a new type of vertical electromagnetic stirring to improve the central quality of continuous casting billets. The results show that the new type of vertical electromagnetic stirring can form a large melt circulation movement up and down in the center of the billet, promote the temperature and composition mixing of the molten steel, and improve the feeding ability of molten steel to the final solidifying zone. So that the central band defects in the special steel billet are greatly improved and eliminated. The mechanism of vertical electromagnetic stirring to promote columnar-to-equiaxed transition and improve the solidification structure is analyzed in this paper. This work was financially supported by NSFC (No. U1760206) and the 111 Project 2.0 of China (No. BP0719037). Correspondent: egwang@mail.neu.edu.cn

The last decade has been characterized by a global set of policies and regulations to prevent and reduce Greenhouses gas emissions. The iron and steel industry is the largest energy-consuming and emitter of CO₂ in the manufacturing sector. However, several studies have demonstrated that by only shifting technology from the BF/BOF to the DRP/EAF can reduce carbon emissions by up to 50%. Moreover, the ENERGIRON Zero Reformer is characterized not only by 45% less CO₂ emissions vs. competing technologies, but also can further increase CO₂ capture up to 90% and commercialize it as a valuable by-product. In this context of worldwide concern climate change, the ENERGIRON technology has become the best solution for steelmakers that want to comply with the most stringent environmental regulations worldwide. Indeed, thanks to his flexibility to use different energy vectors, even 100% Hydrogen and capacity to further sequestrated the CO₂, the ENERGIRON ZR technology is the pioneer for the future iron reduction production. Keywords: DRI, CO₂ emissions, Climate change, Ironmaking, Hydrogen, ENERGIRON, Danieli

The steel industry is known for the large amount of greenhouse gases emitted in the atmosphere in its processes, mainly for the burning of fossil fuels. The sector is responsible for about 10% of all CO2 emitted in the world, which 70% comes from the burning of coal and coke in the blast furnace. In the short term, we have as reality the use of electric steelworks, it means, the production of steel from scrap and other inputs. Electric steelworks are already commonly known and have the advantage that is not necessary burning fossil fuels. However, a high demand for electricity is necessary, which in some countries has a high cost, making the business unfeasible. The use of hydrogen in the production of primary iron has been studied and is pointed as an interesting alternative, although the cost of obtaining it and the forms of use need to be better defined making it a long-term possibility. Another possibility is the use of biomass in the processes, that has been studied and in some small blast furnaces it is used, mainly in Brazil. This is an alternative that can be envisioned in some countries once there is availability of these materials, requiring only some adaptations of processes for implementation. Therefore, this work comes with the purpose of showing some alternatives for the future of steel companies with the increase of emission restrictions, focusing mainly on a short to medium term solution that are biomasses.

Gas carburizing of solid steel is carried out by using much amount of hydrocarbon in order to keep the furnace atmosphere as long as constant, because carbon from hydrocarbon is consumed for carburization of steel surface and hydrogen remains in the furnace. In the present study, selective removal methods of H₂ were surveyed and fundamental experiment was done by using Proton Conductor SrZr_1-xY_xO_3-a , which was prepared by spark plasma sintering method; hydrogen gas was separated from wet simulated coke oven gas atmosphere at high temperature successfully. At the same time, reported method to selectively remove H₂ was also applied to bench scale furnace for gas carburizing of solid steel by using gas filter module made of poli-imido fiber tube. The control of the furnace atmosphere was very important to keep it constant, which was also studied numerically as well as experimentally. Finally, selective removal of H₂ from the furnace was verified experimentally and the flow rate of so-called “carrier gas” (hydrocarbons) could be reduced more than 75 % under the condition of the same quality of steel surface by the carburization treatment. As a result, exhaust gas volume could also be reduced and the burnt exhaust gas, namely, CO₂ emission was minimized.

There was about 1.28 billion tons of hot metal produced in 2019 with various operations of blast furnaces around the world. The present paper describes similarities and differences in BF operation based on hands on experience and operational results. The focus is on large blast furnaces (≥12 m hearth, ≥3200 m3 IV). The paper starts with comparing results in productivity, coke rate and total fuel rate. A comparison is made of:
(1) the effect of BF size on operation results, (2) raw materials being used, slag volume and composition as well as the effect of slag volume on PCI rates and productivity, (3) operating philosophies: consistent versus variable blast volume, (4) Tuyere parameters like velocity and blast momentum, (5) PCI rates and oxygen enrichment, and (6) use of burden distribution.for optimizing BF operations which includes the ferrous and coke layers that are being used as well as methods for using two sizes of sinter. In the discussion the authors address the question what operators can learn from each other.

As part of the European Community’s Ultra-Low Carbon Dioxide Steelmaking (ULCOS) program, blast furnace top gas recycling was tested to reduce CO2 emissions using the LKAB experimental blast furnace. During tests from 2007-2010, the blast carbon rate was reduced by about 25% when CO recovered from blast furnace top gas was re-injected into the furnace stack using a second bustle pipe. Hatch and BHP have re-visited the top gas cycling concept to assess if additional technologies such as hydrogen and hot oxygen injection could be implemented to further reduce CO2 emissions beyond what was achieved at the experimental blast furnace. Using a 2-stage heat and mass balance model, viable operating conditions were established for a low carbon rate operation, significantly less than what was achieved in the ULCOS trials. Details of the enabling technologies to reach such low CO2 emission rates will be presented.

The reduction of greenhouse gas (GHG) emissions, especially carbon dioxide (CO2) is becoming critical in the steel industry. The natural gas based MIDREX® Process paired with an electric arc furnace (EAF) has the lowest CO2 emissions of any ore-based steelmaking route with options to lower even further. As ‘green’ hydrogen (electrolysis source using renewable electricity) becomes available, it can be injected in the MIDREX Process with minimal modifications, thus reducing emissions further. Ultimately, MIDREX H2™ will make use of hydrogen both as the energy source and the reductant to produce a near-zero carbon footprint metallic, which can be used as feedstock in hydrogen steelmaking. Unfortunately, ‘green’ hydrogen is not available today at sufficient scale and low enough cost for rapid adoption. Additionally, the capital requirements to convert from the blast furnace-basic oxygen furnace (BF-BOF) route to direct reduction-electric arc furnace (DR-EAF) steel production are prohibitive. Therefore, the rapid conversion to hydrogen steelmaking is unrealistic, so other ways to reduce CO2 emissions during the transition phase must be explored, such as the use of HBI in a BF.
Hot Briquetted Iron (HBI) is a compacted form of Direct Reduced Iron (DRI) that is manufactured with well-defined, consistent chemical and physical characteristics that make it very suitable for handling, shipping, and storage with minimal yield losses during those steps. HBI can be used in an EAF to produce high quality steel products and in Blast Furnaces to increase productivity and lower coke consumption, ultimately lowering CO2 emissions. As a merchant product, HBI can be produced in large scale operations at a location where logistics and reducing gas (including hydrogen) can be advantageous and transported in the right amount to existing steelmaking complexes. As such, HBI produced outside of one’s facility should be considered in all steelmaking operations as a flexible metallic source during the hydrogen transition.

Some studies have shown that the use of biogas in steel companies can be very useful. Since the biogas could be the substitute of coke (this requires coking coal) and non-coking coal that is injected into the tuyeres which are essential materials in the production of hot metal and consequently in the production of steel, the biogas can also come to allow the reduction of the production cost of iron and steel consequently. The objective of this paper is to do an economic survey of the biogas which can be used at steel companies. The research consists of raising costs of production of biogas from where it is manufactured (farms and small producers) through the cost of logistics transportation and storage until to the end consumer (steel plants). The idea is to study the possible substitution of natural gas, to guarantee the high temperature compared with the normal process, by using the biogas. In this subject, it can be developed a thermal balance where the biogas volume will be calculated to have the final profile, same as using natural gas. Additionally, it will be shown that the next step is to provide the Direct Reduction Process to use Biogas in substitution of Natural Gas. Based on the amount of the residues given by Cattle Breeding, it can be concluded that the Iron and Steel production in the World can achieve an amount of two thousand million tons of Steel yearly, only using the biogas with no coke, no charcoal, no Natural Gas. This is our big challenge for this century.
Key-Words: Environment, Sustainability, Blast Furnace, Biogas, Natural Gas, Coke rate

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