Present day, the production of hot metal (HM) via the blast furnace route remains an integral part of the global steel industry. With global pressure to curb greenhouse gas emissions, injection of hydrogen is considered a promising solution while ironmaking transitions to alternate technologies. A comprehensive heat and mass balance model calibrated to an operating blast furnace was used to assess the operational limits of hydrogen injection through the tuyeres, replacing Pulverised Coal Injection (PCI). Constrained by a minimum top gas temperature and minimum Raceway Adiabatic Flame Temperature (RAFT), the maximum injection rate was determined to be 19.5 kg-H 2 /t-HM when replacing 37.4 kg-PCI/t-HM (i.e. a replacement ratio of 1.9 kg-PCI/kg-H 2 or 1.54 kg-C/kg-H 2 ). At the maximum hydrogen injection rate, the specific CO 2,eq emissions were seen to decrease by 8% in the top gas. In the case where the increased level of hydrogen increases stack reduction efficiency, the maximum hydrogen injection rate is decreased, while the replacement ratio is increased significantly. A maximum hydrogen injection rate of 14.3 kg-H 2 /t-HM with a replacement ratio of 4.5 kg-PCI/kg-H 2 was achieved when the stack reduction efficiency was 100%, with a CO 2,eq emission decrease of 14%. The optimal scenario for injection of hydrogen was determined to be maintaining a constant production rate, allowing the RAFT to decrease, and replacing PCI.

Softening and Melting (S&M) experiments have evolved alongside the blast furnace as a crucial tool for burden characterisation and optimisation. Modern blast furnaces derive a base load of hydrogen from various sources. However, with hydrogen-enrichment of the blast furnace being considered to mitigate emissions, new S&M test conditions are required. In this study, a 2-D axisymmetric CFD model is used to simulate the internal conditions of a modern blast furnace operation, and a future operation with tuyere level hydrogen injection. The model results are used to guide the development of novel S&M test conditions, inclusive of H 2 , H 2 O, CO, CO 2 and N 2 . The maximum hydrogen concentration under hydrogen enrichment was 20%, with the hydrogenous fraction of the gas primarily replacing nitrogen. A particular focus was given to the importance of including water vapour in the inlet gas, andits impact on reactions occurring in the S&M test.

Hydrogen-enriched blast furnace (BF) operation is currently being assessed to mitigate greenhouse gas emissions while the steelmaking industry transitions to low carbon emission technologies. Increasing the usage of lump ore in the BF also presents opportunity to decrease carbon emissions, as it can be directly charged to the furnace without agglomeration. Use of lump ore in modern blast furnace operations is facilitated by high temperature interactions with sinter. With more emphasis on hydrogen enrichment in BF operations, the behaviour of lump and sinter mixed burdens must be characterised under new conditions. In this study, 15% hydrogen is added to the standard gas conditions of a Softening and Melting (S&M) apparatus (replacing nitrogen). Analysis of auxiliary reactions such as the Boudouard Reaction and the Water-Gas Shift Reaction is presented and their impact on burden reduction and performance assessed. Results indicate that with the inclusion of hydrogen, the performance of sinter burden deteriorates, while lump burden shows significant improvement. Interaction between sinter and lump still occurred with the inclusion of hydrogen in the gas, and the mixed burden behaviour of 20% lump and 80% sinter fell between that of the individual burdens. From interrupted experiments, it is noted at high degrees of reduction, the lump burden forms a solid metallic layer which maintains its interparticle voidage at high temperatures, supressing exudation of liquid slag.