Abstract
The present work explores computationally the potential of hybrid operation of a direct reduction shaft furnace with a feed gas mixture of methane and hydrogen, considering the operation of the associated gas handling and conversion units (reformers, condensers, heat exchangers, compressors, heaters, etc.). The state of the system is dependent on both the performance of the shaft furnace, which is sensitive to the feed gas composition and quantity, and the reformer, which converts the methane and the recycled top gas from the shaft furnace into feed gas. This coupling gives rise to nonlinear behavior of the system with respect to changes in the boundary conditions, which justifies a model-based approach for holistic analysis. The system is modelled in Aspen Plus to simulate the operation of an industrial-scale plant using a detailed model of the process units. Three configurations of the system are evaluated: (i) co-feeding of hydrogen with methane, (ii) feeding hydrogen directly to the shaft furnace, and (iii) splitting the hydrogen feed between the two injection points. Further, the effect of H2 share in the feed was evaluated in terms of energy consumption, CO2 emissions and energy cost with low- and relatively high-carbon electricity. The results show that increasing the share of hydrogen in the fresh feed leads to lower CO2 emissions, considering low-carbon electricity.