Reduction kinetics of in-flight molten hematite particle in the HIsarna process

The energy and environment issues have been paid more and more attention by the iron and steel making industry. During the past few decades, a number of new breakthrough technologies for iron and steel making have been developed by different countries to achieve a significant reduction in CO2 emission and energy consumption. HIsarna is one of the technologies which belongs to ULCOS (Ultra Low CO2 Steelmaking) program in Europe and aims to cut CO2 emission by 80% per ton of steel with Carbon Capture and Storage (CCS) technology. HIsarna process makes use of coal and iron ore fines directly as raw materials instead of coke and pellet. It combines a melting cyclone and a smelting reduction vessel (SRV) into a single smelting furnace. The fine hematite ore undergoes a series of complex chemical and physical changes while descending in the melting cyclone such as thermal decomposition, gas-solid particle reduction, melting, and gas-molten particle reduction. It has been found that the hematite particles can melt down quickly in the reducing gas when the temperature is higher than 1650K. The objective of this study is to investigate the reduction kinetics of in-flight molten hematite particle at the typical conditions of melting cyclone. The experiments have been carried out by using a high temperature drop tube furnace. The reduction was accompanied by thermal decomposition reaction during the first 210ms. The kinetic analysis showed that the unreacted shrinking core model could be used to characterize the reduction and thermal decomposition process. The activity energy of the gas-molten particle reduction was about 156kJ/mol-1. Keywords: HIsarna process, gas-molten particle reduction, thermal decomposition, reduction kinetics, high temperature, fine hematite ore