Improving the Installed Base and Enhancing Operations
Steel production differs significantly from plant to plant in terms of efficiencies and operational practices. Integrated steel plants for example vary widely in energy consumption depending on the basic technologies they employ.
Along the production value chain the largest absolute differences in energy consumption generally occur in the ironmaking phase because blast furnaces consume varying amounts of reducing agents reflecting differing qualities of sinter coke and pellets as well as different operating modes. There are also large variations in fuel consumption among hot stoves based on their respective modes of operation.
The largest relative deviations are generally in the steelmaking phase owing to missing or nonexistent gas recovery from basic oxygen furnaces inefficient operation modes or inadequate automation of electric arc furnaces. Outdated technologies such as open-hearth furnaces and ingot casting also consume considerable amounts of energy. In addition inefficient reheating furnaces limited hot charging or inefficient drive systems can increase energy consumption in the solid phase.
The large differences in consumption of reducing agents in blast furnaces are particularly interesting. According to Stahlinstitut VDEhan association of the German steel industrybest-practice blast furnaces in Germany today are operating close to the physical limits dictated by the process of reducing ferrous oxide employing carbon-based fuels. Nonetheless there is still significant potential for improving blast-furnace-based steelmaking. Many producers around the world are still far from meeting best-practice standards in either blast furnace technology or operations. The plants that have the most room for improvement are commonly located in RDEs but not only there; and many producers in RDEs are far from laggards with respect to energy consumption. On the contrary many of the most modern plants in the world have recently been built in RDEs. For example the blast furnace of a first-class producer in China has the lowest energy consumption of all the representative plants shown in Exhibit 10.
Comparisons like those in Exhibit 10 do not necessarily reflect realistic potentials for improvement because producers operate in conditions that are to some degree beyond their control. For example larger plants are generally more efficient than smaller ones; this is particularly true of blast furnaces. Similarly the cost quality and availability of input factors such as local transportation and scrap all influence the efficiency of the process. So in assessing a particular companys potential for improvement it is necessary to take into account the unique boundary conditions of the production sites involved.
How much improvement is possible in steelmaking worldwide? If the entire current installed base of integrated steel plants and minimills were to adopt existing best practices we estimate that the theoretical improvement potential would be a reduction of more than 4 exajoules or about 20 percent of global steelmakers annual energy consumption (based on 2006 consumption levels). This reduction in energy use would also mean producing some 600 million tons less CO2 annually. (We projected these results to the global installed base from a benchmarking analysis of some 30 producers worldwide. The projection is based on 2006 capacity dataand on the assumption that capacity added since then has been state-of-the-art.)
Of course theoretical estimates rarely coincide with realistic possibilities. Taking into account the physical economic and political conditions in which actual steel plants operate we expect that it should be possible to realize some 50 to 70 percent of this potential. This means that more than 2 exajoules could be saved from annual energy consumption of the global steel industry and more than 300 million tons of annual CO2 emissions could be avoided.
From our recent work with steel producers and their suppliers around the globe as well as from our discussions with industry and technology experts we have learned that it is possible to achieve the performance improvements cited above by employing existing technology. A major lever for reducing energy use is the direct improvement of the individual aggregates that go into the steelmaking process. For example new state-of-the-art technologies to agglomerate the inputs for the blast furnace not only consume considerably less energy than older ones but also create higher-quality coke or sinter contributing to lower energy consumption in the blast furnace.
In addition modern automation systems can be used to minimize the superfluous use of energyboth by optimizing the operation modes of individual production units such as blast furnaces and electric arc furnaces and by improving production logistics along the whole process chain.
A significant lever for reducing net energy consumption is energy recovery. Especially in the liquid phase of the steelmaking process large quantities of superfluous energy can be recovered in the form of heat pressure and caloric value (of exhaust gases). These forms of energy can be reused in other process steps as sources of heat or electrical power. In this context the improved management and design of energy networksfor power gases or steamallow steelmakers to save additional energy. They can realize further improvements by employing modern drive systems that combine highly efficient drives with state-of-the-art automation.