Calix’s Zero Emissions Steel TechnologY (ZESTY) is designed to help decarbonise one of the world’s most carbon-intensive industrial processes – iron and steel production. The industry accounts for ~7-9% of global CO2 emissions, with the majority resulting from the use of metallurgical coal in the reduction of iron ore to metallic iron.
ZESTY enables direct hydrogen reduction of iron ore (H-DRI) in a renewably powered reactor to produce green iron and ultimately, green steel. It provides the potential for a zero-carbon route to iron and steel that in turn can help add value to local iron ore exports, future-proof local iron and steel production and support sustainable global development.
ZESTY’s indirect heating approach is well suited for electrification, including with renewable and intermittent energy sources. Electrification also means no combustion. With ZESTY, hydrogen is consumed only as a reductant, not as a fuel, and can be simply recycled in the process. This key feature enables ZESTY to target the most efficient and economical use possible of hydrogen.
Pilot-scale testing shows that Calix’s ZESTY technology can produce a hydrogen direct reduced iron or “H-DRI” product approaching commercial grade.
Excellent metallisation (conversion of iron ore to iron) was achieved for Siderite and Goethite / Hematite ores. ZESTY’s compatibility with small particle sizes was found to facilitate fast rates of metallisation, allowing for significantly shorter residence times and lower temperature operation than a conventional blast furnace. Hematite makes up 96% of Australia’s exported iron ore and is not otherwise suited to most electric arc furnace (EAF) methods.
Reduction and metallisation extents for the non-porous and dense magnetite sample were lower, reaching a maximum metallisation degree of 54% at 1050°C. An increase in residence time and/or temperature for the processing of dense, non-porous magnetite samples is expected to lead to improved reduction and metallisation of magnetite by ZESTY.
An expanded testing program, using a range of ore types from Australia and overseas, has commenced. Further planned pilot-plant modifications will enable continued exploration of critical performance parameters, as well as ore selection and pre- and post-processing requirements.
The ongoing R&D program is informing a Front-End Engineering Design (FEED) study for a 30,000 tonne per annum, zero CO2 emissions ZESTY-iron demonstration plant. The FEED study is supported by a A$947,035 grant from the Australian Government’s Australian Renewable Energy Agency (ARENA) and is expected to be completed by the end of 2023.
 M. Shahabuddin, G. Brooks, and M. A. Rhamdhani, J Clean Prod, 136391 (2023) 395