Hydrogenation of Various Iron Carbonates and Room-Temperature Pyrophoricity of Reduced Solid Iron in a Fluidized Bed

Thermal decomposition of iron carbonate in the steel industry is one of the major sources of industrial CO 2 emissions. Hydrogenation of iron carbonate using renewable-driven green hydrogen (H 2 ) serves a transformative strategy for in situ CO 2 utilization by coupling iron production. In this study, we focus on the hydrogenation behavior of various iron carbonates in a fluidized bed using siderite as the raw material, as well as on the room-temperature pyrophoricity of the resulting reduced iron as a fundamental step related to iron-based zero-carbon fuel applications. The effects of siderite type, reaction atmosphere, and hydrogenation temperature during the hydrogenation process on the distribution of resulting gaseous products are systematically investigated using a thermogravimetric analyzer (TGA) and a fluidized bed reactor. Hydrogenation reduced the starting decomposition temperature of siderites by 50–100 °C and increased the decomposition rate. At temperatures below 400 °C, CO was mainly derived from the direct hydrogenation of siderite, and its yield increased with hydrogenation temperature. CH 4 was entirely generated from the direct hydrogenation of siderite, with its yield peaked at 400–450 °C. Metallic iron was the primary iron phase after hydrogenation of siderite. At temperatures above 450 °C, metallic iron exhibited catalytic effects on the reverse water-gas shift (RWGS) reaction of CO 2 . At room temperature, metallic iron was highly reactive and quickly oxidized by O 2, leading to pyrophoricity. The peak temperatures during the pyrophoricity process were primarily influenced by the porous structure after hydrogenation and the O 2 concentration. Meanwhile, microexplosions were observed during the pyrophoricity process.