Energy efficiency and CO 2 emissions reduction in the steel industry

Transcription

1 Marlene Arens (Fraunhofer Institute for Systems and Innovation Research) Energy efficiency and CO 2 emissions reduction in the steel industry EFONET WORKSHOP 4.3 Increasing energy efficiency in industrial processes Berlin, February 19th 2010

2 2 Introduction The Iron and Steel Industry is one of the biggest industrial CO 2 emitters. Globally, between 4 and 7% of the anthropogenic CO 2 emissions originate from this industry. CO 2 reductions in the iron and steel industry are essential if governmental climate protection targets are to be achieved. Energy Consumption in the Iron and Steel Industry Currently, there are two main iron and steel making processes in the EU. The first one is the blast furnace route, also called the primary route as it converts iron ore into pig iron with the help of reducing agents. The main reducing agent is coke, which is produced from coal. Other reducing agents are pulverized coal, waste plastics or oil. The remaining carbon in the pig iron is oxidized in the basic oxygen furnace with the help of oxygen. Crude steel remains. The other main route, the electric arc furnace route or secondary route uses scrap as the input and melts it with electricity. Since the most energy-intensive step in iron and steel making is the reduction of iron ore to pig iron, the secondary route is less energy-intensive. It needs just one third of the energy required in the primary route. There are two other less common iron and steel making processes. Direct reduction uses natural gas as a reducing agent and reduces iron ore in its solid state. The resulting product is called direct reduced iron, which then requires further treatment in the basic oxygen furnace, or which can substitute scrap in the electric arc furnace. As this process needs large amounts of natural gas, it is mainly applied in countries which have a cheap supply of natural gas. In Western Europe, therefore, there is only one such direct reduction plant. The fourth technology used to produce iron and steel is the smelting reduction process. Iron ore and coal are smelted in a vessel to directly produce pig iron. As this is able to process non-coking coal and fine ores instead of coke, sinter and pellets, it needs less energy than the blast furnace route. The technology has a rather long history of development, but there is only one commercially available process, which still requires certain shares of coke. Several other technologies are under development. There is the need for reliable indicators to compare the energy efficiency of various countries especially in the case of a global climate protection agreement. At present, only the specific energy consumption for the iron and steel industry is published. As this does not differentiate energy consumption by the different production routes, it is difficult or even impossible to make statements about the energy efficiency of the iron and steel industries. A higher ratio of electric arc furnace steel reduces the specific energy consumption of a country. From an energetic point of view, an increase in the production of EAF-steel could be favorable, because

3 3 this is less energy-intensive. But there are limitations: Firstly, scrap is also a resource with restricted availability. Secondly, not all the steel qualities desired can be produced using EAF. Especially copper alloys cannot be removed from scrap. Experts therefore believe that the primary route will remain one of the most important iron and steel making processes in the future. Options for energy efficiency in the Steel Industry The blast furnace technology is more than 100 years old. As a result, it has been constantly refined over the decades and the specific use of reducing agents has been lowered. It is frequently stated that blast furnaces are already operating at their energetic theoretical minimum. Still some experts claim that there is a further energy consumption reduction potential here of 10 to 15%. In the literature, several saving options for the blast furnace are being discussed, such as pulverized coal injection, use of scrap, improved heat recovery and improved process control. One promising technology for steel casting is the Castrip technology, which processes coils in just one step from liquid steel. It eliminates several reheating steps and therefore reduces the energy consumption by three quarters compared to thick slab casting, and by one half compared to thin slab casting. CCS in the Steel Industry the Ulcos Project Carbon Capture and Storage (CCS) is currently being discussed as a future technology to drastically reduce CO 2 emissions. The Ulcos project was set up to apply this technology in the European iron and steel industry. It aims to reduce the CO 2 emissions of today's best routes by at least 50% by applying CCS to iron and steelmaking technologies, such as blast furnaces, direct reduction and smelting reduction. The project also includes research on the electrolysis of iron ore. This technology could produce iron without CO 2 emissions or the need for CCS if the required electricity could be produced in a CO 2 -free way. Due to its early stage of development, this is not expected until 2040 at the earliest. Several problems have to be solved, the huge amount of electricity required being one of the biggest obstacles. Therefore this technology depends on the introduction of a hydrogen economy, or fusion technology. Among the Ulcos technologies, blast furnaces with CCS represent the technology which has been developed the furthest. Oxygen is injected into the blast furnace to support the production of CO and CO 2. The CO 2 is then removed from the top gas and stored geologically. The remaining CO is reinjected into the blast furnace thereby reducing the amount of reducing agents needed. In 2009, a pilot plant was built in Eisenhüttenstadt, Germany. A demonstration plant will be built in Florange, France, in Commercialization is predicted for 2040.

4 4 The Hisarna process is a smelting reduction technology with CCS. It requires neither coke, nor sinter and pellets. A pilot plant is due to be built in Ijmuiden, Netherlands, in New production processes which do not require coke, sinter or pellets Smelting reduction processes have been under development for over two decades and are said to be the only viable contender to the blast furnace in iron making (Luiten 2001). Iron ore fines and non-coking coals are smelted in a vessel to directly produce pig iron. As neither coke nor sinter nor pelletizing is necessary, both energy consumption and CO 2 emissions could be roughly 10% lower than in a blast furnace. Only one process has reached commercialization so far, but this still requires certain amounts of coke. Other processes which can do without coke are close to commercialization. Future technological strategies in the European steel industry From the viewpoint of energy efficiency and climate protection, the current technological options in the iron and steel industry can be structured in three routes which leads to path dependencies to some extent. The first option aims to improve energy efficiency in the blast furnace route and an increased use of electric arc furnaces. This strategy applies all the current best available technologies. Therefore, its R&D risks are rather low. The second strategy builds on Carbon Capture and Storage which is still uncertain as so far it is not definite that CCS will be applied in the future. Furthermore, even if this is the case, CCS should only be applied to plants which are working at their theoretical energetical minimum. If there are further improvements in energy efficiency - even if this is only 10% - these potentials should be realized before the use of CCS. CCS will always require more energy than current processes, as the sequestration of the CO 2 and its storage as well as further equipment is needed. Currently there are no available estimations on the additional amount of energy. The third technological possibility is a diffusion of the smelting reduction technology, which reduces both energy consumption and CO 2 emissions.

5 5 Literature Kirschen, M., Badr, K., Cappel, J., Drescher, A.: A cost-effective method to reduce energy consumption and CO 2 emissions in steelmaking. Stahl und Eisen 129 (2009), Nr. 9. Luiten, E.: Beyond Energy Efficiency. Dissertation. Utrecht University, Advantages with the Castrip process. Stahl und Eisen 129 (2009), Nr. 9. Orth, A., Anastasijevic, N., Eichberger, H.: Low CO 2 Emission Technologies for Iron and Steelmaking as well as Titania Slag Production. Materials, Minerals, & Metal Ecology Schlichting, M., Ondrovic, J., Woodberry, P., Michael, D.: Energy and environmental Wirtschaftsvereinigung Stahl, Stahlinstitut VDEh: Statistisches Jahrbuch der Stahlindustrie 2008/2009 Zulianti, D. J., Scipolo, V., Born, C.: Opportunities to reduce costs and lower GHG emissions in EAF and BOF steelmaking. Stahl und Eisen 129 (2009), Nr. 9.