Study of cluster formation during powerfailure in a green hydrogen counter-current moving bed reactor

Sammanfattning

The steel industry must shift from a carbon-intensive process for production of steel to achieve a long-term sustainable process. One promising approach is to use green hydrogen produced by electrolysis of water to separate it into hydrogen and oxygen. This study investigates the mechanisms behind cluster formation and how the relationship between temperature, gas composition, pellet quality including shape and size, and reduction degree might affect sticking. Calculations for reaction rates show that there is a decline of the reaction rate with falling temperatures. The theoretical calculations suggest that the temperature of the hourly production equivalent could be reduced significantly, assuming the reduction reaction is ongoing. Then a simplified CFD-DEM model was simulated, and the data were analysed as a one-dimensional system. The model results show the same trend as the theoretical calculations, indicating that as an order-of-magnitude estimate, the temperature of a part of the bed material could be reduced by gas circulation. The material, or parts of it, could potentially be converted into a final product with enough stored hydrogen. The results suggest that utilizing the remaining gas may improve plant output and decrease the remaining heat for a safer shutdown. The alternative is to burn the process gas by flaring. These findings provide a foundation for future work of defining an algorithm for dynamically predicting sticking risk.