New Insights Into Hydrogen Reduction of Hematite in an Indirectly Heated Flash Reactor from Measurements and First-Order Modeling

Abstract New pilot-scale experimental data are reported for hematite reduction with hydrogen in an indirectly heated flash reactor, named the Zero Emission Steel Technology (ZESTY) reactor, together with analysis with a one-dimensional well-stirred reactor and kinetic model. The process feeds particles by gravity through a tubular reactor, which is indirectly heated through the walls that are maintained at a range of uniform temperatures from 850 to 1100 °C to achieve metallization of up to 95 pct. Process modeling is performed with Aspen Plus utilizing two kinetic models, namely the modified Sohn and mixed control models, together with a number of assumptions. The kinetic parameters are then adjusted with experimental data to best match the measured conversion. Calculations for hematite particle residence times consider particle velocity within the reactor, alongside particle size with the density modified to account for conversion extent. The modified model provides a reasonable match of the increase in the metallization degree of hematite with rising temperatures across the range of operating conditions. Moreover, elevating the hydrogen stoichiometric ratio correlates with increased metallization degree. Also as expected, an increase in the particle size adversely influences the metallization degree through decreasing the residence time. The level of agreement and internal consistency increases confidence in the reported results and interpretation of the measurements.