Authors: F. Wheeler, F. Atkinson, I. Gordon, S. Broek, V. So, M. Barati
Abstract
As part of the on-going development of the Hatch CRISP (Continuous Reduced Iron Steelmaking Process) technology, a series of pilot test heats was carried out in a four-day period during the week of August 27th, 2007 on the 8-tonne AC electric arc furnace at the facilities of the MEFOS Metallurgical Research Institute in Luleå, Sweden. The main objective of this series of tests was to examine the interaction between slags of a selected range of compositions with a steel bath continuously charged with DRI. Analysis of the results from the fourteen trial heats at MEFOS confirmed the viability of the CRISP technology.
The key findings from the test program can be summarized as follows:
- It is possible to produce low-carbon steel (below 0.10 %C) with a good foaming slag
and low FeO (below 18-20%) and without the use of gaseous oxygen
- No major refractory erosion was experienced under these conditions
- Stable and reproducible operating conditions can be achieved
- The relationship between bath carbon and slag FeO and basicity for a non-gaseous
oxygen scenario is established
These findings make it possible to define a window of operating parameters for the CRISP process. This represents a milestone in the development of the CRISP technology.
In addition, the following benefits of the CRISP technology were confirmed:
- The slag FeO / bath carbon dependence is closer to equilibrium than that experienced in conventional EAF operations. This leads to improved metallic yields and lower slag volume and related flux consumption
- The nitrogen content in the bath approached levels experienced in oxygen steelmaking- between 22 and 34 ppm
This paper summarizes the results and conclusions from the pilot trials in August, 2007. As part of the ongoing development of the CRISP technology, a second series of pilot tests is scheduled at MEFOS for April, 2008. These trials will closely approximate the projected CRISP operation with DRI continuously melted over a period of several days.
