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The world steel industry is going through a significant restructuring period. This is the time when the old gives way to the new, the less productive to the productive, the inefficient to the efficient. The restructuring is creating expanded opportunities for the electric arc furnace, mainly at the expense of the open hearth furnace - but in some cases, the basic oxygen furnace as well.
Open hearth steelmaking outside the USSR and China has largely been replaced by the EAF and BOF processes. In fact, the EAF has passed the open hearth as the second most widely used steelmaking furnace.
Now the EAF is gaining ground on the BOF for the industry lead. Among the reasons for the growth of EAF steelmaking is the shift in capacity from developed countries, whose steel requirements supported the large-scale production of the blast furnace/basic oxygen furnace route, to newly developed countries, whose present steel requirements and future needs are best served by the direct reduction-electric arc furnace route.
BF/BOF
Over the past decade the blast furnace/basic oxygen furnace (BF/BOF) combination has been the dominant steelmaking route in the world. There is no doubt that this technology has made a significant contribution to improving efficiency, productivity and product quality in the production of steel.
The blast furnace has been used for ironmaking for over 600 years. Optimisation of the technology has reached an extremely high level with implementation of improvements such as burden distribution, hydrocarbon injection, pulverised coal injection, increased blast temperature, oxygen enrichment of the blast, increased hearth diameter, high top pressure and recovery of energy in the top gas.
The basic oxygen furnace was developed approximately 30 years ago. Since that time great strides have been made with process improvements such as combined blowing, dynamic control, suppressed combustion, inert gas stirring, submerged injection of lime and coal fines and recovery of energy in the off-gas.
As with most technology, the refinement of the BF/BOF steelmaking route has resulted in greater complexity and higher capital cost. Regardless of the large number of improvements that have taken place in BF/BOF technology, there are still limitations which are unlikely to be resolved. Some of the limitations are outlined below:
1 Large number of unit operations. In addition to a...