Direct Reduced Ironmaking Technology: Hot Briquetting Trials of DRI with Higher Carbon Levels

by Vincent Chevrier, PhD., Christopher Ravenscroft

Publisher - Midrex Technologies, Inc.

Category - Engineering & IT

Steelmakers have greatly increased the use of carbon as an energy source in the EAF to reduce electricity consumption and increase productivity. Ore-based metallics like pig iron and direct reduced iron (DRI) are frequently added to the EAF scrap charge for their pure iron units in EAF steelmaking, but these products can also provide those additional carbon units. Hot briquetted iron (HBI), a denser compacted form of DRI, is also used in the EAF, but HBI has been historically produced in the 1 - 2% carbon range because up until recently increasing carbon levels beyond that range would lower the briquetting temperature, and in turn lower productivity. Midrex developed the patented Adjustable Carbon Technology (ACT™) to produce DRI with higher carbon levels without loss of temperature in the lower part of the direct reduction shaft furnace. This technology is available for both existing and new MIDREX® Plants, and can be a unique differentiator for merchant HBI plants: HBI quality can be tailored to the specific needs of the customer and yet maintain a very high yield during transportation and during melting. The clear benefit of ACT™ for HBI plants is to increase carbon while maintaining briquetting temperature; however, it is currently not possible to study the impact of increased carbon (at a given temperature) on HBI properties in commercial plants. To minimize the scale up risks associated with ACT™ for HBI plants, the Midrex Research and Technology Development Center undertook a series of tests at bench and pilot scale. The study shows that while there is a measurable reduction in both density and strength of the HBI as carbon increases, the HBI maintains adequate strength over a wide range of carbon. The first commercial implementation of this system is currently slated for North America’s HBI facility that Midrex is building for Cleveland Cliffs in Toledo, Ohio, which will be able to supply highquality customized HBI to the Great Lakes region of North America.

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