Project description

The steel industry's CO2-emissions can be significantly reduced by switching from the carbon-based blast furnace route to the predominantly hydrogen-based direct reduction route. In direct reduction, iron ore pellets are reduced to iron in a counter-current reactor using reducing gases. With the use of natural gas as a reducing gas, direct reduction is already state of the art in industry. However, the increased use of hydrogen as a reducing gas changes the reduction and carburization reactions and thus the optimum operating conditions in the reactor. These changes are to be simulated in the project.

A particle-resolved CFD simulation (PRCFD) is being developed for direct reduction in order to be able to investigate the processes within the pellets and in the gas phase flowing around them in detail. This enables a transient simulation of the local momentum, heat and mass transport as well as the mapping of chemical reactions in the pellet and in the gas phase. As part of a multiscale approach, a kinetic 3D model of a single porous pellet was first developed. This model depicts the heterogeneous reactions with changing gas and solid compositions as well as porosities, pore diffusion and temperature development locally and transiently in the pellet. By coupling this kinetic model with the gas phase using the PRCFD, external flow effects and homogeneous gas phase reactions can be taken into account. The PRCFD is to be repeated for sections of the various zones in the direct reduction in order to map the respective reaction conditions and pellet properties. This allows the influence of gas composition and velocities, temperature, pressure, pellet size, porosity and tortuosity to be investigated.