CRISP Technology

Numerous advancements have been made in the DRI-based steelmaking processes in the last decade. Charging hot DRI to the electric arc furnace (EAF), directly from a DR module is arguably the most important improvement in this area. The energy saving associated with the hot charge practice is estimated around 20 to 30% compared to the current cold-fed EAFs. Nevertheless, continuous discharge of hot DRI to EAF is complicated by the batch operation nature of the EAFs.

Continuous Reduced Iron Steelmaking Process (CRISP) is a novel steelmaking technology, being developed by Hatch that utilizes a stationary electric arc furnace to continuously melt and decarburize DRI and other metallic materials to produce steel. The key feature of CRISP technology is significant modification of the conventional EAF process parameters to extend the refectory life beyond one year.

The flowsheet of CRISP is shown in Figure 1. As depicted, DRI is produced in the DR or reduction furnace and fed to the furnace, along with scrap and iron oxide. The charge materials are fed continuously into the CRISP furnace that is essentially a six in-line electrode stationary EAF. Continuously operated CRISP EAF close links two processes: DRI production in the reduction furnace and continuous casting.

Figure 1: Flow diagram of a CRISP plant

The decarburization of DRI is accomplished with zero gaseous oxygen and through the oxidation by slag; that is supplied with iron oxide as ore lump, pellet or mill scale. Since the charge is introduced into the furnace continuously, it is critical to adjust the specific rate of material feeding in order to meet the requirements for sufficient decarburization inside the furnace. Steel and slag are periodically tapped out through slag and metal top-holes in a similar approach to BF. After steel is tapped out, the remainder of the process is similar to the conventional steelmaking including ladle refining and casting.

Figure 2: Schematic diagram of CRISP furnace

The essence of the unique features of the CRISP technology is:

These differences lead to significant operational benefits, the most important being:

References

1. M. Barati, J. Li, et al: Slag engineering aspects of the CRISP steelmaking technology, Accessed JAN 2019;

2. E. S. Kiasaraei: Decarburization and melting behavior of direct-reduced iron pellets in steelmaking slag, MSc thesis, University of Toronto, Canada, 2010, Accessed JAN 2019;

3. F. Wheeler, Y. Gordon, S. Broek, I. Cameron: The successful piloting of CRISP, The successful piloting of CRISP, the innovative continuous steelmaking technology, La Metallurgia Italiana, No2, 2010, p.27-33.