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Hot metal production in the blast furnace from the ecological point of view
Abstract
The blast furnace is the classical iron ore reduction process based on carbon. Iron ore reduction with carbon inevitably leads to process-related unavoidable CO 2 emissions. Before the background of the efforts to reduce the emission of green house gases and of the coming CO 2 emission trading within the EU, the blast furnace process is evaluated regarding existing potentials to reduce CO 2 emissions. Possible potentials to reduce the reductant consumption and by this the CO 2 emissions was evaluated by the use of a blast furnace balance model developed by ThyssenKrupp Stahl AG.
... c The values are from [40], except for labor requirements and gas consumption. The gas consumption value for BF is from [79]. d The process includes steam turbines for power generation. ...
... e All values are from [84], except for labor requirements and gas consumption. The gas consumption value is from [79]. f CO 2 capture rates for air-blown BF are based on the carbon flows indicated in [79], and an assumption of CO 2 /CO molar ratio of 1:1 as suggested in, e.g. ...
... The gas consumption value is from [79]. f CO 2 capture rates for air-blown BF are based on the carbon flows indicated in [79], and an assumption of CO 2 /CO molar ratio of 1:1 as suggested in, e.g. [6,85]. ...
... The potential consequences of this assumption are discussed in Section 8. The reference iron and steel production process is taken from previous work (Kuramochi et al., 2012), which is based on a typical German BF presented in Schmöle and Lüngen (2004). The average reductant consumption of German BFs is similar to the plants in the EU-15 (Schmöle and Lüngen, 2004), which accounts for most of the integrated steelmaking plant capacity in the EU-27. ...
... The reference iron and steel production process is taken from previous work (Kuramochi et al., 2012), which is based on a typical German BF presented in Schmöle and Lüngen (2004). The average reductant consumption of German BFs is similar to the plants in the EU-15 (Schmöle and Lüngen, 2004), which accounts for most of the integrated steelmaking plant capacity in the EU-27. Therefore , it is considered this reference to be representative of European integrated steelmaking plants. ...
This study assesses whether the deployment of CO2 capture technologies in the European industrial sector would result in significant changes in the emissions of air pollutants (NOx, SO2, PM, and NH3) in the short term. The industrial sectors investigated were: cement, petroleum refineries, and iron and steel. The analysis included onsite emissions and changes associated with grid electricity consumption due to CO2 capture. Post-combustion capture using monoethanolamine (MEA) was considered for the cement sector and petroleum refineries, and Top Gas Recycling Blast Furnace (TGRBF) with vacuum-pressure swing adsorption (VPSA) for the iron and steel sector.The results show that when all three industrial sectors in the EU-27 are fully equipped with CO2 capture, industrial SO2 emissions in the EU-27 may decrease by 40–70% whereas NH3 emissions may increase by 120–520% (equivalent to 2–8% of total European emissions). The large increase in NH3 emissions is due to the degradation of MEA. Cement and petroleum refineries account for nearly all these changes. The results also show limited impact (within ±10% of EU-27 industrial emissions) on NOx and PM emissions. Emission changes due to electricity import/export are found to be equally important as onsite emission changes. For the iron and steel sector, the changes in National Emissions Ceilings Directive (NECD) emissions are found to be limited for the selected CO2 capture technique under conservative assumptions. However, the changes in the NECD emissions could vary largely depending on how the steel mill will adapt and operate their coke oven batteries that supply the coke to the blast furnace (BF).
... Attempts to decrease dependency of metallurgical coke and consequently reduce the CO 2 emission are for large extent based on the following approaches; (1) substituting coke with H 2 -rich carbon-bearing materials; (2) producing agglomerates from secondary resources; and (3) shifting the iron oxide reduction process toward lower carbon utilization Continuous development connected to reducing coke consumption in, for example, the BF has been always under investigation. Such development resulted in a decrease in coke consumption bỹ 60% since 1960 [7]. Coke has been partially replaced by other alternative carbon sources (pulverized coal, natural gas, etc.) through the BF tuyeres over years and such replacement is now practiced in all modern BFs. ...
The iron and steel industry is still dependent on fossil coking coal. About 70% of the total steel production relies directly on fossil coal and coke inputs. Therefore, steel production contributes by ~7% of the global CO2 emission. The reduction of CO2 emission has been given highest priority by the iron- and steel-making sector due to the commitment of governments to mitigate CO2 emission according to Kyoto protocol. Utilization of auxiliary carbonaceous materials in the blast furnace and other iron-making technologies is one of the most efficient options to reduce the coke consumption and, consequently, the CO2 emission. The present review gives an insight of the trends in the applications of auxiliary carbon-bearing material in iron-making processes. Partial substitution of top charged coke by nut coke, lump charcoal, or carbon composite agglomerates were found to not only decrease the dependency on virgin fossil carbon, but also improve the blast furnace performance and increase the productivity. Partial or complete substitution of pulverized coal by waste plastics or renewable carbon-bearing materials like waste plastics or biomass help in mitigating the CO2 emission due to its high H2 content compared to fossil carbon. Injecting such reactive materials results in improved combustion and reduced coke consumption. Moreover, utilization of integrated steel plant fines and gases becomes necessary to achieve profitability to steel mill operation from both economic and environmental aspects. Recycling of such results in recovering the valuable components and thereby decrease the energy consumption and the need of landfills at the steel plants as well as reduce the consumption of virgin materials and reduce CO2 emission. On the other hand, developed technologies for iron-making rather than blast furnace opens a window and provide a good opportunity to utilize auxiliary carbon-bearing materials that are difficult to utilize in conventional blast furnace iron-making.
... The integrated steelmaking process using BF is expected to keep on playing a dominant role in the industry in the longer term [25]. The production efficiency of BF is not expected to improve significantly because it is already very [26]. Regarding CO 2 capture, some advanced technologies are proposed in the literature. ...
This paper presents the methodology and the preliminary results of a techno-economic assessment of CCS implementation on the iron and steel sector. The results show that for the short-mid term, a CO2 avoidance cost of less than 50 € /tonne at a CO2 avoidance rate of around 50% are possible by converting the conventional blast furnace (BF) to Top Gas Recycling Blast Furnace (TGRBF). However, large additional power consumption for CO2 removal and oxygen generation, and reduction in BF gas export, makes the economic performance of the technology very sensitive to energy prices. Add-on CO2 capture for conventional BF may achieve similar costs (40–50 € /t CO2 avoided), but the CO2 avoidance rate will be only about 15% of the specific CO2 emissions. For the long term future, although there are large uncertainties, advanced CO2 capture technologies do not seem to have significant economic advantages over conventional technologies. The results also indicate that in a carbon-constrained society, when considering new plants, smelting reduction technologies such as the COREX process, may become a strong competitor to conventional blast furnace based steel making process when equipped with CO2 capture. Although conventional iron and steel making using BF is expected to dominate the market in the long term, strong need for drastic CO2 emissions reduction may drive the sector towards large scale implementation of advanced smelting reduction technologies.
The Chapter examines the features of operation of small blast furnaces on coke and charcoal, theoretical and practical aspects of design and operation of small blast furnaces. Due to the lack of literary data on the operation of small blast furnaces for smelting ferroalloys, the Chapter provides a general description of the state of affairs in this branch of metallurgy and details the theoretical and practical aspects of smelting ferromanganese by small blast furnaces. An overview of known implemented projects in the world is provided.
The Chapter gives the characteristics of small blast furnaces and the comparison of large and small blast furnaces, estimates the number of furnaces in the world that can be classified as small, and the distribution by the main operating countries. A brief overview of the development of small furnaces in Europe, Brazil, Russia and countries of the former Soviet Union, China, India and ASEAN is given, taking into account regional characteristics, including the main process fuel, charge materials, the target product as well as the challenges facing blast furnaces and shaft recycling units. A preliminary conclusion has been made on the prospects for using mini blast furnaces in different regions. A case study of a mini blast furnace operating on 100% briquette charge is described.
All chemically used carbon in the blast furnace will be emitted as carbondioxid to the atmosphere after energetic use of the carbonmonoxid and carbondioxid containing blast furnace gas (top gas) and after processing of the carbon containing hot metal. On occasion of the emission trading the question arises whether the blast furnace can be operated without coke and carbon and without CO 2 emission. To answer this question the physical and chemical tasks of the coke in the blast furnace as well as the limits for the use of hydrogen as reducing agent in the blast furnace are shown.
The growing production of hot metal - in due relation to the demand - forms the basis of the world's increasing demand for steel. In this context the blast furnace process will remain the number one ore reduction process. In Germany hot metal and crude steel are produced on a competitive basis at several integrated steel works using blast furnaces and basic oxygen converters which are world leading in terms of plant technology and operation. Within the framework of research programs, the development of an oxygen blast furnace process is underway, which - in combination with a CO2 capture and storage (CCS) system - is expected to massively reduce CO2 emissions from hot metal making. Direct reduction processes produce solid direct reduced iron (DRI) from iron ore without the use of coke. DRI is mostly used as input material in electric steelmaking. The majority of the DRI is produced in gas-based processes, especially at locations where low-cost natural gas is available. The intention of coal-based smelting reduction processes is to produce liquid hot metal without or only with very small amounts of coke. Of the various technologies, the Corex and the Finex processes have so far been applied to industrial-scale production. Whereas the Corex process relies on the use of lumpy ore charge, Finex can be operated with fine ores. Both processes will require the CCS technology to achieve a substantial reduction in CO 2 emissions.
The ULCOS blast furnace process (ULCOS BF) aims at minimizing the CO 2 emission of the blast furnace by at least 50 %. This process is based on the replacement of hot blast by cold oxygen, the recycling of decarbonated top gas into the lower shaft and normal tuyères, the capture of CO 2 and its storage in a geological trap (full CCS process). The ULCOS blast furnace concept has been demonstrated during three campaigns at the LKAB Experimental Blast Furnace in Luleå, Sweden. Following the success of these trials, the construction of a demonstration unit is currently under progress.
The coke plant/blast furnace will remain dominant for the production route from iron ores to crude steel. There exists a community of fate for the coke plant and the blast furnace as blast furnaces cannot be operated without coke for physical reasons. For cost optimization, it was and is important to minimize the coke rate in the blast furnace and to utilize the by-products of the blast furnace and of the coking plant. The paper discusses, for an interconnecting network of an integrated iron and steelworks, the potentials of the use of coke oven gas and blast furnace gas. The coke oven gas can be utilized for electric power and heat production, for conversion into hydrogen and methanol as well as reducing gas in the blast furnace or in a DRI plant. Blast furnace gas can be used conventionally for blast heating, coke plant underfiring and power production, or it can be recycled to the blast furnace in the nitrogen-free blast furnace process and in the plasma heated blast furnace process. A critical comprehensive assessment is also given for these potentials with respect to CO 2 emissions.
Die Stahlindustrie in Deutschland gehört aufgrund des Reduktionsmittelbedarfs an Kohlenstoff für ihre metallurgischen Stoffumwandlungsprozesse und ihrer hohen Erzeugungsmenge von rd. 45 Mio. t Rohstahl pro Jahr zu den energieintensiven CO2-emittierenden Branchen. Sie hat sich gegenüber der Bundesregierung verpflichtet, ihre spezifischen Kohlendioxid-Emissionen bis zum Jahr 2012 um 22 Prozent gegenüber dem Referenzjahr 1990 zu verringern. Maßnahmen zur Verringerung der CO2-Emissionen beziehen sich auf die Erhöhung der Energie- und Ressourceneffizienz. Viel versprechende neue Anstze mit erheblichem CO2-Minderungspotenzial bietet die Weiterverarbeitung von Rohstahl zu Walzstahl. Zukunftstechnologien und langfristige Maßnahmen für die Klimavorsorge stellen die Wasserstofftechnologie zur Roheisen- und Stahlerzeugung sowie die Hochtemperaturelektrolyse von Eisenerz mit CO2-unbelasteter elektrischer Energie dar. Innerhalb der Wertschöpfungsketten tragen neue Stahlwerkstoffe zu einer weiteren Verminderung von CO2-Emissionen bei.
The injection of different auxiliary reducing agents into the tuyeres of a blast furnace has fundamental effects on the metallurgical reactions and on the total energy and material balance of the process. For a comparison of the different tuxiliary reducing agents it is of utmost importance to determine the changes of all balance values and to take all effects on the hot metal costs into consideration with an overall approach. Considering the prices for all input materials and the estimated prices for the products of the blast furnace different solutions are possible to realize, in dependence on the circumstances, an optimization in the process and plant technique, a minimization of the hot metal costs and therefore integrated approaches.