According to Sustainability Report, 2008 steel is produced by the following methods:
• Combination of the blast furnace (BF) and basic oxygen furnace (BOF). In this process the raw materials such as iron ore, coal, limestone and recycled scrap steels are used.
• Electric arc furnace (EAF) approach based on the recycled steel scrap and/ or DRI and electricity input.
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Figure 8-2 BOF/EAF methods used to produce steel in 2007 (Sustainability report, 2008)
In steel production, firstly iron is made and it is charged into EAF or BOF for melting. Scrap is also charged as raw material and melted. After steel has been made in the EAF or BOF, it is transferred to a ladle in which refining operations and the addition of alloying elements are performed. From the ladle, steel is passed to the continuous-caster machine. Here semi-finished products such as slabs are produced. Finally semi-semi-finished steel is processed in rolling mills and turned into finished products (Fenton, 2005). More detailed explanation of the processes will be explained in the following parts.
8.6.1 Iron-making
Iron is produced from iron ore either by blast furnaces or direct reduction. In our case, DRI plant will be located in the cluster and iron production will be done by this method. Therefore we think that it is more appropriate to explain DRI. Iron ore is reduced to solid iron by reducing gases (CO and H2) when producing DRI. The temperature in the shaft and the composition of the reducing gas influence the reduction speed and rate. The output from the conversion is Fe (in addition to oxidated reducing gases). It can be in the form of lump, briquettes and pellets. In addition, CO2 and H2O (as well as CO and H2) are output from the shaft. Parts of this gas are recycled together with new methane gas to produce more reducing gas.
DRI is efficiently used by continuous charging through the EAF. It is especially valuable to make high-grade steel because the unwanted elements are lower than those scrap normally contains. It is used to control the quality, however, more expensive than scrap.
BOF/EAF m ethods used to produce steel in 2007
68%
32%
BOF EAF
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In this process, DRI and/ or scrap are converted into steel by a refining process that reduces carbon and silicon content and removes impurities. It has been already determined that EAF will be the structured approach to be used in the steel plant of the cluster. Thus, we will describe EAF process.
EAFs have the most recent technology in steelmaking and have an important advantage of operating with a cold charge in which scrap can be used up to 100 percent. DRI is a substitute for scrap and used to produce high-grade steel. Quality can be controlled by usage of EAF.
Another advantage of the EAF process is its relatively low capital cost per ton of steel produced.
In EAF, firstly raw materials are melted and refined in a second vessel. Carbon is removed from molten steel by argon-oxygen-decarburization (AOD) process or reduced into the required low level by oxygen lancing method. Insertion of the ferrous-alloys is done in this process in order to provide the required mechanical properties.
8.6.3 Casting
Steel is poured from ladle into continuous-casting machine where it is cut into billets, blooms or slabs. Continuous-casting machines have the following components; water-cooled copper mold; a cooling chamber; pinch rolls and rollers for supporting the casting. A steel plant contains an EAF and thin-slab caster has a much lower investment cost, and less energy is consumed to reheat the slab.
8.6.4 Rolling and Finishing
From continuous casting machine slabs, billets and blooms are passed through hot and cold rollers in the rolling mill in order to produce finished products.
Figure 8-3 Steel production process
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9 FORECASTING OF THE DEMAND
This chapter will familiarize the reader with the different forecasting methods used in business. Then, based on the theory we will make the forecasting for demand of crude steel in Norway. Since the potential plant is considered to be ready for production in following years it is essential to implement reliable estimation methods for the demand of crude steel. It is obvious that demand is the driving force of business.
We believe that accurate forecasting of demand may influence on the design of the plant in terms of capacity. In addition, it will reduce the uncertainty in decision making as well as make better estimation for the future. There are many ways to forecast future but we will implement quantitative methods rather than qualitative ones.
By this work, our primary goal is to implement applicable and practical forecasting methods to contribute decision making process for the future plant. Secondly we can use the forecasting results as reliable demand data while testing our mathematical models.
Since the steel demand in Norway is one of the goals to be satisfied by the potential industrial cluster, we have estimated particularly Norway demand. Due to the lack of data, while implementing the methods, we have assumed that the consumption of steel in Norway for the previous years is the historical data for the demand in Norway. Moreover, in this stage the potential steel plant is considered to sell crude steel, therefore the data and forecasting is related to crude steel demand.