Full oxygen blast furnace steelmaking: From direct hydrogen injection to methanized BFG injection

This paper presents a novel concept of Power to Gas in an oxygen blast furnace, through blast furnace gas methanation and direct H2 injection. The PEM electrolyser produces H2, which reacts with the CO and CO2 from the blast furnace gas forming synthetic natural gas. The latter gas is injected into the blast furnace, closing a carbon loop and avoiding CO2 emissions. A parametric analysis is performed to vary the H2:CO2 ratio in the methanation reaction. Different ratios are simulated and compared, among of which the most representative are: (i) 2.5, where unreacted CO2 is directly recycled with the synthetic natural gas; (ii) 4, where stoichiometric conditions are found and the synthetic gas is composed mostly by CH4; and (iii) 8, where an excess of H2 is found in the synthetic gas; and (iv) an infinite ratio, where only H2 is injected in the blast furnace. In the latter, the methanation plant is not required, and no synthetic natural gas is produced. The results show that low H2:CO2 ratios perform poorly, involving high PEM sizes and high costs but only a 5% of CO2 avoidance (compared to conventional blast furnaces). A H2:CO2 ratio of 4 and full H2 injection results in higher reduction of CO2 emissions (33.8 % and 28.6%) with carbon abatement costs of 260 and 245 euro/tCO2, respectively.